Can i install, Parallels 13 + vm (host and guest), on osx high sierra on external hard drive

I need to work on 2 differents imac with the same programs
Best solution for me it's using an external hard drive with host and guest installed.
I could buy 2 licenses but if it needed but i can't install parallels component on osc when i boot from external hard drive.
Can i avoid this problem? i'm still trying with demo version to be sure i can solve this problem.
Can i force components installation?
Thanks in advance
Gigi