What information does BIOS load into RAM?

Question

I know that, on booting, BIOS loads the first sector (512 bytes) of a pre-defined device drive on memory 0x7c00 and then jump to that address.

So, memory from 0x7c00 to

Answer 1

With any remotely recent BIOS, you can obtain memory map information by using the BIOS Int 15/AX=E820h call. This will tell you what memory you can use for your OS.

A more detailed explanation on how to detect available memory, and the contents of the BIOS memory map can be found at OSDev.