Hi, There is no restriction of power supplies for a stack, Stack can operate with all switches having single power supply, but if you want for a redundancy purpose, you can have two power supplies. Thanks, Prabha

Process of election is same, when a master is lost, member switch with highest priority, if the priority is same, switch with lowest mac address is elected as master

2960Xr Flexstack cables are not power capable

15.2(2)E4 is the recommended release for 2960S

2960x and 2960XR cannot be stacked, as they both have different license