I. Requires more than one memory element to accept the given $L$ Non-CFL
II. Requires more than one memory element to accept the given $L$ Non-CFL
III. The given Language Accepted by one-Stack PDA
Let $m=2, \: n=1$
Then $w=abbccd$
Push all a's and b's in to the stack and for every c pop one b from stack and for every d pop a from stack. After processing the complete input stack is empty and is accepted by PDA. So that the given language is CFL.
IV. The given Language Accepted by one-Stack PDA,CFL.
I and II are not CFLs.