what a foolish comment this is!.Sanskrit is the oldest living language of India simply because it's all pervasive in modern day Indian languages (even Tamil has borrowed).
Going by the discovered manuscripts and literary works, Rigveda is considered the oldest 1500BC, and hence onceagian Sanskrit takes the crown of Oldest language.
Kannada, has the oldest inscripts (Nishadi) from the Proto-Old Kannada days. Also the oldest Tamil inscription dating back to 350BC has generous Kannada words (refer the scholar Iravatham Mahadevan). So in all essence of the oldest language, Sanskrit certainly is. Of the oldest spoken languages in India, Kannada and not Tamil takes the crown.
dear friend mahadeva
first you must know the history of languages. then come to the topic. do you know the first grammenr book for old or new kannada language. but we know for our(tamil) language that is first in b.c 9850(agathiyam) and secound in b.c 1500(tolkaapiyam) but sanskrit had grammer in b.c 500(panini) only. and you must know another thing there are lot of tamil words in rig veda ( b.c 1500) so in
b.c 350 tamil , kannada , sanskrit words are here and there are not pointable things