finding maximum virtual and physical memory
No, you can't get size of physical memory with the provided information.

Explanation:


Virtual memory that you mentioned is correct. But you can calculate
it just by seeing the number of bits virtual address has (What you
did is correct though).
To calculate the physical memory, we need to know that Physical memory is a collection of frames, which has same size as pages. Since
Page size is already given (4KB), next we need to know how many
frames does main memory(physical) has. For this we need to know the
size of page table entry, which contains frame address. If we know frame
address length, then we can calculate the total number of frames by
calculating  2^(length of frame address). 
Then you can multiply the frame size (4KB) with the above value to get the size of Physical memory.