and try test recover OS to a USB ext HDD disk(can I with simply backup?)

ATI 2016 BETA

My PC - Win 8.1 Pro - boots from USB in case.

In case do an backup - and try test recover OS to a USB ext HDD disk(can I with simply backup? Or needed other kind? Or cannot recover to ext hdd?)... then try to boot from USB HDD ext the WIN81PRO then, I will be able(Windows license OK - same PC?)?
Again boot from ext HDD but Not delete my actual HDD Win 81 Pro boot c:/ drive and after shut down from USB ext HDD boot normally from main internal HDD.

this is to test recover OS/Apps/Data before upgrade to win 10 pro.

During restore - I must finish restore - and boot from ext hdd - correct?