How to reset iMac pro with a Windows keyboard

[RUEBOi]

Start iMac pro white screen Then applr logo appears then 20 aexc later a no or Lock symbol will appear right below that the loading icon stays searching I guess it's in safe mode or some other easy solution
loading mode

 

[BadAsAl]

A circle with a line through it means it cannot read the hard drive to boot it.
Is the lock you are seeing a lock symbol with a password box below? That means the iMac is firmware locked and you will need the password from whomever set that up.

The first one might mean the hard drive is bad or the OS needs to be reinstalled. The second one means it is a brick unless you can get that password.