Led on when plugged on Cat6A Eth cable?

When plugged with PoE adapter (with its power adapter) does the “power” led light if the Eth cable is disconnected?
Does the led light if I plug the Eth cable (Cat6a) on PoE adapter but not in the Mikrotik device?
Do I have to use only Cat6A cable?
How do I check if the device is powered?

When plugged with PoE adapter (with its power adapter) does the “power” led light if the Eth cable is disconnected?

yes

Does the led light if I plug the Eth cable (Cat6a) on PoE adapter but not in the Mikrotik device?

yes (i dont see the difference with your first question)

Do I have to use only Cat6A cable?

No

How do I check if the device is powered?

Power led, beeper, computer etc…