My answer to your questions.
1a) You cannot connect monitor into com port. But you can connect the monitor directly to the motherboard with other 2 ports. There are two ports that can be connected HDMI and D-sub (
https://imgur.com/a/yCYuE).
1b) Yes, you can if you connect everything right.
2) If another motherboard is the same ASRock H81 PRO BTC R2.0 then there is no problem.
Best practice is to make windows configuration on one ring and then clone the hard drive. Then the cloned hard drive you can put on another motherboard with no problem. But the motherboard should be the same as you cloned.
For cloning software, I can suggest Macrium Reflect or Clonezilla. But you can use any software you like.