Do I understand the RAM device correctly?

Question

RAM

Do I freely understand the device of RAM? I will write with a number of simplifications to make sure that I adequately understand the basic level.
1. Each process has access to a 32 (or 64) bit address space.
2. Each process communicates with memory through a special layer (memory manager)
3. When switching between processes, each process is given its own address space
3.1 Where and how the set of address spaces is stored, I still don’t
understand heap with stack.
4.1 The stack stores data and addresses of functions with their parameters
4.2 There can be only one stack per process
4.3 Green threads / fibers (and their analogues) are good because they work within the same stack segment and do not create a new one, i. time is saved on point 3.
Please write where I'm right, where I'm wrong, and that is the feeling that somewhere I misunderstand very much.

Answer 1

You are wrong in not specifying the OS.
"The stack stores data and addresses of functions with their parameters" - addresses are the same data. And the code is the same data, and it can also be stored and executed on the stack. Moreover, the same data can be both a valid address and a valid code.
You need to read Tanenbaum and Rusinovich, and at the same time something on the protected mode of the processor.