i purchased the tagtool a while ago, and i like it much better than the new one.
If i have to reset/reinstall my ipad, or buy a new one(mine is severely broken), will i be able to reinstall the older Version of the tagtool?
The old Tagtool has been removed from the App Store. Your only option is to back up the existing copy of the App from your iPad to your Mac (using iTunes), then restore it to your new (or reset) iPad. Also make sure you don’t upgrade to iOS 11.
Actually, the old app is not available on the App Store anymore, but you can still download it if you bought it before. You can always go to the App Store (on the iPad) and re-install the old version under the “Purchased” tab. As @thp said: take care not to upgrade to iOS 11, as the old version is only compatible till incl. iOS 10!