With a self-hosted license, you are entitled to 1 Live URL and 1 Test URL (the Test URL cannot be public facing).
You can use your Test URL to test your upgrade process at a different URL than your Live URL. As the Test URL, by policy, can only be reset when the Live URL's domain is reset, I would recommend making this test upgrade instance a sub-domain on your Live URL's domain. E.g. if your Live URL's domain is example.com then I would recommend making your Test URL's sub-domain test.example.com (or similar).
This way, you do not need to reset anything and once you are ready to go live, you can point your Live URL to where your upgrade is and move forward. Then moving forward, should you need the Test URL, it is available at test.example.com (or whatever sub-domain you chose).