No, I don't believe you're missing anything. The Tones part of the store seems to only be on available when on iOS. It's been a while since that change; can't say I have the slightest idea why, but it is what it is I suppose.
You can still sync custom ringtones from itunes on your computer, the process is just a little different.
As far as the restrictions on your phone, that's going to be on there until you can put in the code for the restrictions to turn them off. In iOS 12, they've put the Content Restrictions under Settings > Screen Time.
If there is truly no hope of getting/knowing/figuring out that restrictions passcode, the only way to get that gone for good is to Restore the device to factory settings, restoring from a backup is only going to bring those restrictions back again. You could always take some time to try and guess the codes before you pull that trigger though.
Best of luck!