Q1 Answer
The PC is rebooting as it cannot get a response from the CPU. Q2 Answer
The CPUs can be fried, but any modern PSU will shut-off if it detects that its damaged. Q3 Answer
I wouldn't. The bent pins on the first MB can damage the CPU, which in turn can damage the second MB (if the bent pins were on the CPU socket, otherwise go for it!). Q4 Answer
#Q1 Answer# The PC is rebooting as it cannot get a response from the CPU. #Q2 Answer# The CPUs can be fried, but any modern PSU will shut-off if it detects that its damaged. #Q3 Answer# I wouldn't. The bent pins on the first MB can damage the CPU, which in turn can damage the second MB (if the bent pins were on the CPU socket, otherwise go for it!). #Q4 Answer# EvenEven the most seasoned enthusiast makes mistakes. Have you checked that all connections are firmly secured? Have you also checked compatibility?