I have problem visualising the problem.

Can someone draw schematic for me for problem 2) and draw componentsfor problem 3) so I can understand what is happening here?

 

You need to show YOUR best effort to solve YOUR homework problem. We can then use that is a starting point to discuss with you how you might proceed toward the correct solution.

 

And what do not understand? Start by drawing a schematic of your problem. That often help. Consider the output resistance as a series resistor. And the input resistance as resistance going from the input to the ground. Also picture no current will go into the amplifier it self