Do not update or it reverts to the free version. Wise Registry Cleaner Pro is a relatively small app with folders added to Program Files (x86) & Users\ [UserName]\ AppData\ Roaming\ . It gets 2 registry keys for the app, & one for uninstall -- Note: I recorded a huge number of new entries, and it's possible I missed something. The app has an option to create a portable version, which is portable with the exception of adding one registry key for the app -- as above that's to the best of my knowledge as again a Huge number of new registry entries were recorded, & I could have missed something. The app itself allows to backup the registry, defrag the registry -- basically rewriting it, skipping any blank spaces -- has a tab where you can log in to chat with an unspecified AI, has a tab with alleged Windows system tweaks, and its main purpose, delete registry entries with broken links.
The portable version in particular might come in handy to back up the registry before doing something you might want to undo, considering Windows System Retore is unreliable. Yeah, you'd be better off performing a disk / partition image backup, but you can't always, or may not want to spend the time & effort. Defragging the registry isn't going to hurt anything, and in a pinch cleaning the registry might help, or it might hurt.
The registry itself was Microsoft's solution to problems getting software to run &/or stay running in Windows 3.1, where you either had to be expert at editing Autoexec.bat, Config.sys, & however many .ini files, or have access to someone who was expert at it. It then grew, morphed into the evil monster it is today. Windows registry contains old entries from old code in Windows and other software, many that have been forgotten but live on in code repositories that are still used as the base for new stuff, entries that use the registry in ways that were never intended, and unfortunately, sometimes malware. [One trick is to break a malware script into pieces that are stored separately in the registry & then pieced together and run.] There is no tool to repair or fix the registry -- one simply doesn't exist, or rather cannot exist since there's no right or wrong when it comes to what's entered in a key or value. Reinstalling Windows -- running Windows setup from within Windows, keeping all your files & settings -- helps, but it won't always remove what needs removing... sometimes the only cure is wiping the disk and starting fresh -- one reason Microsoft pushes its OneDrive Backup.
So why clean the registry?... registry cleaners remove entries that point to something that does not exist, whether that's a file or another registry entry. If enough of those entries exist, removing them can make a noticeable difference in the overall size of the files containing the registry, and those files can grow large enough to strain hardware resources -- how much is too much depends on the hardware. It takes time for Windows to look for something, whether it's there or not, so removing entries with links may speed things up. Cleaning the registry can also break stuff -- software may not work after a registry cleaning, and sometimes the software that breaks has been causing problems, so the registry cleaner gets credit for fixing Windows.
Should you use a registry cleaner?... if you 1st perform a disk / partition image backup that you know for certain that you can restore, it falls under: "Nothing ventured, nothing gained". If it hurts, restore the backup -- if it helps, celebrate your win. And enough people have celebrated wins that you shouldn't listen to the haters, & there are more than plenty of those in our world. That said, spend the time and effort and you can sometimes do better. Where a registry cleaner will only remove one line entries, one at a time, those entries are often part of a key taking up several lines, so if you can delete that entire key, you might have 8 or even 10 times the impact. If you want to remove traces of an app, look through the keys associated with that app, and if there are any GUIDs search for them in regedit -- you can sometimes find several, and if they only pertain to that app, you can probably delete them too. Needless to say, you do want to have a backup ready to restore if things go badly.