Well, here is the issue: how do you define India? I'm assuming, as you are Indian (?) that you are well aware that India has an enormously complex history, and that the word "India" is Latin (although I think originally derived from a Sanskrit term) and India itself is based off of colonial borders. Now, I think the modernness of "India" as a concept can definitely be pushed too far (for example, there is the term Bharata, although it is a word that varies enormously depending on context), but it is important to keep in mind how muddy the waters get applying "Indian" too far back in history and in many ways, it can be compared to the difficulty of calling something "European" far back in history. If you define based on, say, Sanskrit, then what about the Tamil civilizations of South India? If you define it off of Hinduism or religions derived from that, there is the problem that Hinduism and Buddhism have spread far outside of India (is Bali "Indian"?). If you define India as the subcontinent, then the term is rather uninteresting. Now, I'm sure you know this, but I just wanted to lead with it.

EDIT: I'll actually clarify my view here a bit: India as a national identity, that is, the idea of "one India" and Indian people, is modern. The Gupta and the Kalabhras would not have viewed their actions as being towards a greater "India" and probably would have viewed each other as foreigners. But "India/Bharata" as a mutable and changing cultural/conceptual idea is quite old.

So, the first useful way to think of this is "how old is civilization (ie, urban society) in India?" to leave cultural matters aside for now. The earliest known example of agriculture in the subcontinent is at Mehgarh, from about 6500 BCE--this is a bit later than Mesopotamia and Anatolia, but not by much. Interestingly, the "suite" of crops found there are things like wheat and barley, which may mean that agriculture was imported from the Near East, but that does not mean that these were migrants. Ultimately, talking about this period is going to be kind of tricky because the sites are in Balochistan, which is not terribly open to archaeological research at the moment, but there seems to have been actual urbanization by about 5000 BCE, and probably rather earlier.

The Harrappan or Indus Valley Civilization (IVC) is the famous Bronze Age Civilization that begins in about 3000 BCE, flourishing in latter half of the third millennium and disappearing by the middle of the second millennium. This is usually what people pinpoint as the first "Indian" civilization, but drawing a line from it to modern India isn't that simple. Most obviously, there is no continuity in urban culture--there is a significant "gap" between the end of the IVC and the emergence of Sanskritic civilizations from whom we can less problematically trace the origins of "India". While it seems intuitively likely that the former left something that the latter picked up, there is no actual evidence of this and while the state of archaeology in the subcontinent is such that the absence of evidence is not evidence of absence, it seems safe to say that the so-called "Vedic" cultures had a hazy and indirect connection to the IVC at most. You can say that this is the beginning of "Indian Civilization", but this is a complicated statement and it is rather hard to get from there to here, so to speak.

EDIT: It is worth noting, looking over your question again, that there is a theory that the IVC spoke a Dravidian language. This is certainly possible and there is good reason to believe it, but is very much unproved. More importantly, I think it is more or less impossible to make a connection between it and the later Tamil kingdoms of southern India.

The emergence of Sanskritic kingdoms begins by about the sixth century BCE. But we have, unfortunately, another problem, and that is the "Vedic period" described, naturally, by the earliest Sanskrit literature (the very earliest, the Rig Veda, is probably from the late second millennium). It is very difficult to tease out actual fact from these problematic sources, or really to know what to do with them, but the Vedic peoples are linked to the migration/diffusion of Indo-European language into India. That agriculture and urbanization of a sort in India is continuous is undoubted, but the Indo-Aryan "Vedic" groups seem to have been originally nomadic or semi-nomadic, which makes sense when compared to Indo-European migrations into Europe. Starting "Indian Civilization" from them is fair, but when do they start? The Indo-European migration into India seems to have been sometime in the middle second millennium BCE, but it is kind of difficult to characterize this migration. It is kind of problematic to begin "Indian" civilization with it in the same way that it is kind of problematic to begin, say, "Greek" civilization with the Indo-European migration.

EDIT: OK, this paragraph is a bit muddled but I'm not sure how to rewrite it. Please ask for clarification and if I can provide an answer I will.

So, there you have it. This doesn't really answer your question, but hopefully it is a somewhat useful non-answer. I'm mostly getting this from The Oxford Companion of Archaeology, John Keay's India: A History and Dilip Chakrabarti's India: An Archaeological History, which I have read sections of.

Not really an answer to your question, though you might find it interesting---given that you are already doing some research on the topic.

One of the earliest references of Vedic religion can be found indirectly from the Avesta. The Avesta contain sacrificial fire rituals like Yasna. Nearly same ritual can be found in the Vedas under the title Yajna. In fact, many words, phonological artifacts are quite similar between the Avesta and the Vedas.

That being said, you might want to read up on Proto Indo Iranian Religion The current thought on the topic is that, both the Avesta and the Vedas derived from this hypothetical religion and then branched out.

Now, breaking down your question into parts:

• Dravidian Civilization the oldest civilization:I really couldn't find any scientific sources for this claim, so I can't speak on it.

• Vedic claims: The problem is writing was developed only about the 3rd century BC in India. Even then much of the religious texts were not written down. The historical information passed through oral traditions for at least a thousand years (that's the current idea) before being written down. The convention is that, you might be able to trust information based on oral sources only if its less than 100 years old. The more time passes, the more oral traditions/histories become distorted. E.g. The game of telephone.

So we don't (can't?) really know when was the Veda revealed or Rama born. However, using linguistic methods, it seems that the oldest part of Veda (mandala 2 and 5 most probably), was created during the 800 at the most. Of course we have know way of knowing for sure.

Finally I would suggest if you want to create a historical timeline, then read up academic encyclopedic articles (except wikipedia!!) and create one from there.

If you are interested in creating a timeline based on religious claims you might want to ask /r/Hinduism, they might be able to help.