Which is older Carnatic or Hindustani?

Depends upon the tutor.

Telugu is considered the preferred language for many Carnatic music compositions. Telugu is often praised for its natural flow and vowel-rich structure, which is considered particularly well-suited for musical compositions.

There is no age limit to learn music. Interest , passion , observation should be there thats it .These 3 are main to learn any thing.

You should learn classical music because classical music is base; if you learn classically, you also easily sing western or Bollywood or any genre songs.

Trinity of Carnatic music are Sri Thyagaraja swamy, Sri Shyama sastri and Sri muttu swamy deekshitar..after learning basics like sarali swaram, daatu varusa, janta, geethams and Varnas, students can be taught the kritis of the above trinity