Can any monitor be used as a vertical monitor Is there any issue about the viewing angle

Yes, any monitor can be used vertically, provided you have the proper VESA mount for that orientation, and provided you have a method to tell the OS that it is. Ow being used vertically. Some monitor mounts will do this for you. Also some monitors have the ability to sense orientation and change the reported resolution to the computer accordingly. The budget solution would be to change the orientation manually in the OS.