Licence and test website on different domain

I am new. I want to buy a wordpress theme. Can I use the theme whenever the domain changes? Because first I want to test it on my test domain. No multiple use

Every developer might have different rules and restrictions for that. In general, it’s not a problem - you install item on localhost, test it (so you can see how it works, make any custom changes you want, etc.) and when you are ready to deploy a “live” version, you just delete item from old location and start using it on new location. It’s that simple.

In other hand, if item uses some type of activation/verification, you might not be able to activate item on new location until developer “approves” 2nd activation. Hence, you may want to ask developer about this.