1 - Most, I say most, eeproms/flash are erased to logic 1 and programmed to logic 0...Most that isl, but I haven't found one that's the opposite.

2 - I assume nothing, therefore they should read back as $FFFF

3 - mandatory I would think. Otherwise you'd just be OR'ing bits...

4 - Probably by ignoring the lowest significant 2 bits in the address

5. #3

A, B, C - I'm fairly sure you have to do everything in the 4 byte blocks, read, erase, write back...