The last time I checked it was possible to import sound files into the Garage Band app and create ring tones that can be used wherever ringtones can be used. I don't remember the exact method. You should be able to find instructions on YouTube.
There are many ring tone apps in the App Store. I have no suggestion on which one to use, but most of them are probably easier to use for this purpose than Garage Band.
There is an AOL app in the App Store. I have no idea if it is any good, or what sounds it uses. The description says it works with AOL email and news.
You can add AOL email to Apple's Mail app. The sounds are limited to those provided by Apple, or the ones you import (per your previous question). I doubt the provided ones sound anything like AOL. But who knows, maybe you'll like them better.
You can access your PC's files on the iPad, provided you are on the same network, and your PC is set up to share those folders/files. Android generally has more options, and the work more like the Windows files system you are probably used to. The iPad's file managment is more basic, and often seems odd compared to Desktop file managers.
Using the Files app you can Connect to Server using the three dot menu above the folder list. You'll need the SMB address of the PC. This will let any app that uses the standard Files interface access the PC files. Some use other methods to connect. Usually they provide an IP address that you enter in the URL bar of of a web browser on your PC.
Remote (internet0 access to files on your computer is also possible, but I'm not familiar enough with the various methods to offer instructions or advice. It's just easier to keep the files you want on your computers and other devices on a cloud service. iCloud drive works best on the iPad, but both Google Drive and Microsoft's One Drive are usable.
Just because you can access a PC's files on the iPad does not mean you'll be able to use them. You'll need an app or utility that is compatible with the file. Moreover, unlike on a PC files, opening files does not usually open it in a default app. You'll often need to start the app, then open the file from there.
