What is the difference between last index and first index?

#1

both have the same base case and following with same index which is zero

#2

For finding last index of element in increasing stack of recursion you have to add one more variable in function i.e. ans, and initially you pass ans = -1. While give recursive call if you find the element at that index reinitialize ans with that index and make recursive call with new ans and si + 1. At base condition I.e. si == end, you will simply just return the ans.

#3

i am still not able to understand what is the difference between first index and the last index