Beginner's questions on tweaking non-branded Android phone (rooting, update recovery, update rom)
1 : Yes , Android does have many partitions as mentioned Here

2 : By default it's locked unless you unlock it as mentioned Here

3 : Yes , it must be unlocked as mentioned in XDA-Developers's Flashing Guide

4: 

A: No you don't have to

B:It depends on your vendor.

5:Yes, It can as mentioned in XDA-Developers's Root I9100G

6:it might brick your phone but for me it stopped in the middle and it didn't brick.