Ok, let's have a go at this. Doubtless others with access to FCOM will contribute.
1. Yes - no problem.
2. Depends why you are downgraded to Alt Brks. If you are unfortunate enough to have lost GRN + YLO, the you are down to accumulator braking ie 7 applications max 1000psi. But if you are there for some other reason but still have YLO (double BSCU fail?) then you have as much braking as you like but may have to modulate to 1000psi yourself. The ECAM Status Page and the ECAL Wheel Page will tell you what you have.
Over to others!
mcdhu