Once again none of what you wrote has any context to the topic of " did these empires and people exist" . What do you mean by " no they are not" do you seriously believe that Chandragupt , Dhana Nanda ,Chanakya and Ashoka did not exist? I seriously hope not .
Although the topics raised by you have no bearing on the discussion , still I would like to answer .
First and foremost... Nobody is discussing the religion of the emperors of ancient India . Secondly The Maurya Empire was not Buddhist it was Ashoka who became a Buddhist , Chandragupta was not a Buddhist as well and accepted Jainism when he had reached old age . The Maurya Empire had Vedic, Jain and Buddhist influences . So please do not make sweping overgeneralized statements .
Secondly it would do you good to read something about the Aryan Theory instead of typing stupidity here. Let me make some facts clear about the theory
1- The population group previously known as " Aryans" are now renamed as the " Ancient North" nobody calls them" aryans" anymore as its a well established fact that " Aryan" &" Dravidian" are not separate races but sub groups of the same Caucasian race.
2- The population group comprising the ancient North came from Central Asia and Not Persia .
3- There was no " invasion " of any kind hence nothing and nobody was "conquered" . It was not a war but a gradual and natural migration of populations which occurred over a period of several hundred years which as mentioned is a common natural phenomenon .
4- These migrations occurred so back in time that it would be foolish to associate them with any nation states or empires which emerged much -much later in history . Going by your logic the nations of East Africa should claim the whole world as all Humans migrated and populated the world starting from that general region.
5-There was no Afghanistan or India then The region which today makes Afghanistan had Hindu and Buddhist rulers and influences and thus was culturally part of the subcontinent .
As far as Hindi and urdu is concerned well both are indeed the same language with influences from various sanskrit inspired local dialects of north India like Khari Boli , Awadhi , Brij and the new language Persian . Languages do emerge , mix and die with time I fail to see whats so new or strange in this case. Infact the name Hindi and Urdu are fairly recent the actual name of this new language which emerged in and around Delhi was Dehlavi . If one studies old urdu dictionaries it has a lot of Sanskrit words and old Hindi dictionaries has a lot of persian words ...Both are the same language which was later named differently .
The Turks brought in their cultural heritage with them ...well yes this happens all the time ...the British too brought their cultural ideas with them and many of these ideas were adopted by the people of the subcontinent .Here as well I dont see anything terribly new or strange.
As far as the Ghar wapsi is concerned I dont think its of much importance ? Its a political stunt thats all and unfortunately politicians have been using religion for their selfish gains for a long time . Both Hindus and Muslims have been used by them for vote bank politics .