Why can't I modify the base address of an array? Is it because the allocated memory would be lost? in that case, I can make an array using a pointer and change what the pointer points to and the allocated memory would be lost too, then what is the difference?
Arrays are objects all on their own, and not pointers. Consider a simpler object:
int a = 0;
Would you expect to be able to change its address? Of course not. An object is a region of storage with a type. The region of storage is identified by its address, so you won't expect to change it. And arrays are objects too. When you declare
int b[8] = {0};
you declare an object, the size of eight integers, that will occupy some storage. You can't change its address any more than you can change the address of any single int.
You have probably been told that arrays are pointers. But they are not! They may be converted, even implicitly, to a pointer more often than not, but they are still object types. Pointers often stand in for arrays because the address of the first element is enough to reach any other element with pointer arithmetic, but the pointer is not the array object itself. The difference becomes apparent when you inspect their object properties. For instance:
sizeof(b) != sizeof(int*)
The object b is not the size of a pointer, indeed it is the size of 8 integers, likely larger than a pointer.