Q1 : Yes, AMD and Intel systems use the same power supply if they are standard types and not some proprietary branded stuff.
Q2 : If the PSU is a dual standard type, i.e., 115/230V, it generally has a slide switch at the back to change it between the two voltage standards. It's usually marked quite clearly. Some PSUs intended for the Indian market are internally fixed for 230V and there is no switch.
The main connector of a normal ATX PSU has 20 pins, but some recent models have 24 pins. The extra 4 pins provide additional paths for better current flow since modern systems consume a lot of power. If your mobo has a 24-pin connector, it's best to use a PSU with a 24-pin connector. But if necessary, you can still use a 20-pin PSU. The additional 4 pins are simply left unconnected.
