BimmerBoost Step-by-Step

So many threads regarding the BB app and I know these are getting out of hand but as the realization that flash/piggy combo is the next level of evolution for the n54 I was hoping the more experience software people on here can fill in a basic tutorial.

1.) Two methods of flashing
a.) Flash only to control everything including boost
b.) Flash to control everything but boost where a piggy will control boost.

2.) Difference between the xdf and bin file
a.) Bin file is what BB software will read and save as a .org file but is this BIN file modified or not when flashing?
b.) XDF, still unsure where you get the starting point for an xdf file, is it your BIN file I'd assume and you'd use TunerPro to edit?
c.) So if you edit an xdf file, now you have a bin file and xdf file, which should be written using BB to the ECU?

3.) If you have an existing flash on the ECU, I heard it is not recommended to try to flash directly over top and should flash to stock first. Even if this is not necessary, how can you find a stock ECU software in NCS-EXPERT to flash the ECU back to stock. I don't have this because my ECU was flashed with vishnu.

I hate being that guy since I know a lot of this was beat to death but at hundreds of pages on the BB thread it is difficult to accurately get clear answers.

Thanks! Also feel free to impart an addt'l relevant knowledge.