An uninstall followed by a reinstall of DotNetNuke will result in a loss of all current website/portal contents.
You mentioned that you "backed up your SQL Server Info and the entire DotNetNuke directory". Were the backups of the database and the site files done BEFORE you upgraded from v 4.8.0 to v 5.2.2 ? If they were done immediately BEFORE the upgrade from v 4.8.0, I would recommend that you restore the site using the backed up files and database, try to figure what went wrong during the upgrade, and they re attempt the upgrade after making any changes in the procedure. One change would be to upgrade from v 4.8.0 to v 4.9.5 then to the current v 5.2.3.
If the backups were made AFTER the upgrade then you won't be able to roll back to v 4.8.0 and will need to find out what went wrong and try to correct the upgrade issues. In that case, here are some troubleshooting tips and questions for you . . .
1. The screen shot that you show woud appear to be a reinstall of v 5.2.2 done after the upgrade to 5.2.2 failed - hence the same assembly and database version message. Do you recall receiving any errors during the upgrade from v4.8.0 to v 5.2.2 ?
2. Please check the site folder Providers\DataProviders\SqlDataProvider for any non-empty log files. These will have the name "xx.xx.xx.log" where xx.xx.xx represents the version number for which errors were logged during the upgrade.
3. Next we need to get a more detailed error message than the Server Error in "/dotnetnuke" application that you have posted. In your site's web.config file, find the line <customErrors mode="RemoteOnly" /> and change it to
<customErrors mode="Off" />
Note that "Off" begins with an upper case letter "O". Resave the modified web.config file. Then navigate back to the site address in your browser. A more detailed error message should now be shown. Post it here in the forum.
4. If you have database access using a tool such as SQL Server Management Studio Express, please examine the EventLog table for error messages logged at the time of the upgrade and later. The details will be in the LogProperties column as xml text.