Physical and software structures of a HD

Please help in my education:

I have opened an irremediably physically hopeless HD, and found a disk
inside looking similarly like the plastic waffle inside a floppy disk
jacket.

1. Is that 'floppy' disk inside the same from edge to center on both
sides in terms of materials used?

2. Are there physical concentric or whatever tracks already laid out
physically by the manufacturers?

3. Are the Fdisk and Format operations limited in doing their jobs on
the 'floppy' disk, in terms of which tracks to use for what purposes,
like the locations of the MBR and the FAT and the individual files?

4. If the tracks destined by the manufacturers for particular purposes
are physcially defective or damaged, can other tracks not be used at
all?

5. Why don't some smart manufacturers and smart software writers of
Fdisk and Format work together to produce a 'floppy' disk for a hard
disk, so that the tracks can be used selectively and optionally for
the various functions and operations of a hard disk.

In regard to #5, if it is possible, then a damaged area where the MBR
or FAT are located could be switched to other areas...?

Please offer your knowledge for my education.

Susma Rio Sep