Three Questions on Downgrading & RSOD

Hi! I've got three questions which i couldnt find answer for.

Here we go:

1) I heard somewhere you can use e3 flasher only on one console. Is it true? I do have a few consoles to downgrade and I am not really into buying e3 for each of them. ( If it is only for one console - are there any "multi-downgrade" solutions? )

2) When reading guides about e3 flasher, i saw that you need to boot to XMB to make it dump NOR flash. The problem is, the console I want to Downgrade is RSOD. Will that be a problem, anyone had luck to have similiar situation?

3) In case I will succesfully downgrade my RSOD~ console back to 3.55, is it possible to get into FSM and run the lv2diag rsod fixer without any problems?

Thank you for any tips : P