This is not really an intermediate level topic. there's not even a question here. Even if someone would want to help you, it would be impossible since these tasks seem to rely on the fact that you already have some code written - i.e. "modify your arm and leg classes..." - and we don't have that code.
If you want to get the most out of this site, I strongly recommend you read all of
this, but in particular
ShowSomeEffort,
NotACodeMill, and
DoYourOwnHomework.
If you come back with specific, FOCUSED questions, people here will bend over backwards to help you. If you instead post "do my homework for me so I can hang out with my friends and not learn anything", as you seem to have done here, you will mostly be met with resounding silence.
There are only two hard things in computer science: cache invalidation, naming things, and off-by-one errors