Solution explanation not clear

#1

can you please explain the solution

#2

just compress the given sequence and then all you have to do is strt from beginning of sequence and end of sequence simultaneously and check -:
if( a[l] == a[r] ) then return 1 + f(l+1,r-1);
else return 1 + min( f(l,r-1) , f(l+1,r) );

base case will be the if left pointer crosses the right pointer i.e
if( l >= r ) return 0;

#3

what is the intuition behind the solution

#4

After removing duplicates you will see that the intution is same as of finding longest palindromic subsequence.