Does an infernal warlock start with 2 or 3 at wills?
Eldritch Blast, Hellish Rebuke and.........???
I believe you only get 2 (unless you are Human). One of those 2 must be Eldritch Blast and the other must be your pact at-will.
That's determined by race, not pact. Pact determines one of the at-will powers you know. You're free to take one other (or two others, if human) from another pact, or the All at-will (Eldritch Blast).
So an Infernal pact Warlock has to have Hellish Rebuke and can pick any others after that.
Nope.
It's Eldritch Blast (is mandatory), your pact at-will (is mandatory) and after that you -may- pick a third if you're human. You don't get the benefits of having that pact, however.