Comparing old & new NCERTs & Tamil Nadu History books (content-wise)

i) How are the old NCERTs & the new ones different (content-wise)? Is it necessary to go through them if I have already gone through the previous NCERTs?

ii) Also, is there any difference in content of the Tamil Nadu history textbooks of Class 11 & 12 compared to the previous ones (especially Ancient & Medieval History)? 

Kindly help!