Currently I have my working website but want to change it. Can I install and register theme in (for example) mydomain.com/test and after building my new website move it to mydomain.com? Or will this block my theme functionality since it will be linked to diffrent address in evanto market?
No problem. If you’re building on the same domain with WordPress you should also be able to just redirect to your subfolder when you’re ready to go live. I’ve done it many times myself