Setting up a test board for upgrade is fairly easy but time consuming.
Do the same with your database by backing it up to another name like "new347-backup". Start the upgrade if it asks for your license key, add it but remember to use -TESTINSTALL immediately after the license key.
trying this two days i follow every step and after finish install i cant login its say requested url cannot be found also cant register i understand this is not support topic just wonder how you people install this i mean upgrade I don't know if it's already fixed, but a long time ago when I updated from 3.4.6 to 4.0.7 the UTF8 Database Converter 1.1.18 messed my entire database.
Go to Template Tools in the left side panel check all boxes under - Rebuild Master Skin Data click the Rebuild button.
When this is finished click Recache Skin Sets after. Click on Rebuild Global Chaches Cache, Rebuild FURL Cache and then Recache ALL.
All members of the Administrators group for that computer have these permissions, but the permissions can also be granted to other users.