Is there any difference between Indian Tamil and Sri Lankan Tamil?

 Differences are many.

1. Written and Spoken: As Tamil is a diglossic language, the differences between the standard written languages across the globe is minimal but the spoken varieties differ considerably.
2. Iyal, Isai and Nadagam: In the sangam age in Tamil Nadu, the classical form of Tamil is classified into three - Iyal (literature), Isai (music) and Nadagam(theatre). Tamil, in any point in Time and Space, has borrowed the influence of these three in varying propositions. You can see how the dialogues of Tamil films in Sivaji Ganesan era (1970s) and now (2018) changed. So as the Tamil words written in India and a distant Sri Lanka. However these differences are minimal in comparison with spoken language.
3. Indian Tamil Dialects: Coming to dialects - Tamil spoken in India differs every 250 kilometres - Kumari Tamil, Madurai Tamil, Chetti Nadu Tamil, Kongu Tamil, Madras Tamil and many.
4. Sri Lankan Tamil Dialects: It has four dialects. i)Jaffna Tamil - close to Tamil Nadu Tamil II)Batticaloa Tamil is more literary and unique Tamil iii)Negomba Tamil - Fishermen Tamil - bilingual, strongly influenced by sinhala iv)Moors Tamil - Spoken by Moors strongly influenced by Arabic
5. Commonality: The spoken varieties in Sri Lanka although different from those of Tamil Nadu share some common features between the Southern dialects (Kumari, Madurai) of Tamil Nadu and the northern Sri Lankan Tamil dialect, the language of Jaffna. Sri Lankan Tamil dialects retain many words and grammatical forms that are not in everyday use in India, and use many other words slightly differently.
6. Influencers of Indian Tamil: Indian Tamil dialects are influenced by Sanskrit and English.
7. Influencers of Sri Lankan Tamil: Sri Lankan Tamil dialects are inflenced by Portugese, Dutch as well as English and Sinhalese.
8. Conservative: In general, Sri Lankan Tamil is considered to be more conservative than continental Tamil.

Migration History of Sri Lankan Tamil:

Languages get diluted with space and time. But descendents who migrated maintain the purity of the time in which they migrated. That is why it is importnt to understand the migration history. It is outside the purview of the question and given as an information.

#The migration consists broadly in two stages -who arrived in 7th to 10th centuries ago, during Chola Rulers to Anuradhapura mainly soldiers; and during British in 19th century as a trade workers.

Foot Note - The outward Indian migration on an organized scale came during British Rule. The commissioning of railway line in 1860 made the trading easy across India. In overseas, Parsis running into China; Gujaratis into Red Sea, Persian Gulf; Sindworkies into Ports in Americas, Europe. For the Nattukottai Chettiars of Tamil Nadu, the chief investment destination was South East Asia. From around 1830, confined Chettiars in Madras presidency, started exporting their capital to Ceylon(Sri Lanka), Burma (Myanmar), Straits settlement (Singapore, Malacca and Penang) and Indo-China. As per the Indian Estimate, the working funds of Chettiars were deployed 64% in Burma, 20% in Malaya, 11% in Ceylon, 4% in Indo China. Less than 1% is deployed in Madras. Chettiars taken the plantation workers all over the places.

When did South Indians also came to identity themselves as Hindus?

 #My views are based on my limited understanding and limited to Tamil Mandalam.

Part 1 - Hindu

I will go backwards in time line.

#South Indians as Hindus in 20th Century: After world war I, that is after 1920s, eventually, any person of Indian origin (including Tamils) who did not practice Abrahamic religions came to be branded as a Hindu, thereby encompassing a wide range of religious beliefs and practices.

#North Indians as Hindus in 18th Century: Towards the end of the 18th century, the European merchants and colonists referred collectively to the followers of the Dharmic religions in Hindustan — which geographically referred to most parts of the northern Indian subcontinent — as Hindus.

#Land of Hindus as Hindustan in 13th Century:The Arabic term al-Hind, referred to the land of the people who live across the river Indus. From 13th century, the word Hindustan began to be used as a popular alternative name for India, meaning the "land of Hindus".

#People Live Across Indus River as India in 5th Century: The word Hindu or Indu was used by Greeks to denote the country and people living beyond the Indus river. Megasthenes' 'Indica' epitomizes the name for India and Indians around the 5th Century B.C.E

Hindu is the Sanskrit Word and Shindu is the Local word for River Indus.

Part 2 - Tamil Religions

I will go forward in time line.

The Tamil area had an independent existence outside the control of northern empires. The Tamil kings and chiefs were always in conflict with each other mostly over property. The royal courts were mostly places of social gathering rather than places of dispensation of authority; they were centres for distribution of resources.

# Tholkappiam between the 5th century BCE and the 3rd century CE: In Sangam poems, there is relatively meager reference given to religion in general. In the akam songs, Tholkappiar has made reference to deities in the different land divisions:

Thirumal (Vishnu) for mullai (Forest)

Murugan (Karthik) for kurinji (Mountains)

Indhiran (Indra) for marutham (Plains or Agri Lands)

Varunan, for neithal (Sea Shores) and

Kotravai (Sakthi or Kali) for palai (Desert)

#Early Religions after Sangam Period: Gradually the rulers came under the influence of vedic beliefs. Shaivite, Vaishnavism and Shaktism come into existance.

#First Five Centuries: Buddhism, Jainism and Ajvika co-existed with early Shaivite, Vaishnavism and Shaktism. It is just to mention that Ajvika survived for nearly 2,000 years through the 14th century CE in Tamil Nadu. Kalabhras period is termed as “Dark Age” of Tamil History

#6th to 13th Centuries: Saivism and Vaisnavism dominated and replaced Buddhism and Jainism. Some of the earliest temples that are still standing were built during this period by the Pallavas. Rock cut temples were the order of the day.

#13th to 17th Century: Saivism and Vaisnavism dominated. It is one of the Golden periods of Temple Architect. Damaged temples of invaders were rebuilt and new structures built and existing structures were expanded by Vijayanagara Kingdom, Madurai and Tanjavur Naickers.

#18th to 19th Century: It is a chaos in Tamil Land - full of conflicts among Local Polygars of Maduari, Tiruchi, Senji, Marathas, Nawabs, British, French.

Christianity and Islam co-existed with majority Saivism and Vaisnavism (together were over 88%). Christians are mainly concentrated in Southern districts - Kanyakumari, Tirunelveli and Tuticorin.

#Post Independence: The trauma of the partition did not impact Tamil Nadu when India was granted Independence in 1947. There was no sectarian violence against various religions. There had always been an atmosphere of mutual respect and peaceful coexistence between all religions in Tamil Nadu.

Do Tamil Brahmins [Iyers and Iyengars] consider themselves to be Aryans or Dravidians?

 

1. Iyers and Iyengars are caste names, whereas Aryans and Dravidians are race names. The former is relavant in day to day usage whereas the latter is relavant for researchers who work on races and confuse the mass with their own theories..
2. Iyers and Iyengars are Tamilians.
3. The division as found in North, like Samvedi, Dubey, Trivedi, Chaturvedi, Pandey, Mishra do not exist in Tamil Nadu.
4. Iyers follow advaitam and Iyengars follow vishistatvaitam.
5. Once Kanchi was epitome of learning on the lines of Nalanda and Takshila and Sanskrit was also a School of Study. Intelligents, they learned this scientific language so introduced to some of their children. They are neither good at it like North Indians and their Vedic Rituals are as well inferior to North Indian Brahmins as the language is still foreign to them.
6. They are respectable communities in Tamil Nadu. Both the names originate from the same respectable tamil root - “Ayya”
7. Later years saw few Iyers migrated to Karnataka(Mysore) and Kerala (Palakkad).
8. Iyengars are also migrated to Karnataka, called Hebbar Iyengars and Mandyam Iyengars. They are grand.
9. Within Iyengars, there is a division - Vadakalai and Thenkalai.
10. Iyers and Iyengars Tamil are much superior than Brahims of rest of India in intellect.
11. Jamshad Chethirakath, a Keralite is known by stage name Arya and Rahul Dravid is a Marathi. Tamils are also crazy in keeping their names as Stalin, Bose etc