1. am+nbncm . it is not Regular.
it is CFL.
we can rewrite am+nbncm as amanbncm
am depends on cm and an depends on bn
So it is not Regular
PDA Design
1. Push all 'a' into Stack.
2. Pop 1 'a' for 1 'b'.
3. Pop 1 'a' for 1'c'.
If String is empty and Stack is also empty, String is accepted.
2.anb3^n n>=1
it is not regular not also not CFL.