Sigil: City of Doors

Does corpse crafter affect:

1) staves that summon I II III IV etc

2) feats like fiendish legacy summon

3) warlock undead summon invocation

4) anything else I am not thinking of?

Yes but only for you. Someone who doesn't have corpse crafter will get the normal summons for their alignment.

Yes

No, warlocks just summon bonecrusher if I remember right

All summon scrolls will default to undead as well (except for stuff like gate, planar ally, etc).

Corpse Crafter converts Summon Monster I to IX to make undead variant, regardless of the source. Fiendish Legacy is Summon Monster V with a fancy name, so it gets converted. Anything which isn't Summon Monster I to IX doesn't get converted, regardless of source.

Cool thanks all! :)