Q: What happened to my paid for application Iphoto for IOS 8?

The new operating system iOS 8 is very different from the previous iOS 7. The way photos are stored on your iPad or iPhone has changed completely. When you installed the new system, you made it impossible for iPhoto to run.  iPhoto need iOS 7.

You can migrate your photos to the new Photos.app as described here:  Migrating from iPhoto for iOS to Photos on iOS 8

and Get help finding your Photos in iOS 8

When i sync to my pc, the ëdited photos"are saved like normal, with no visual changes applied.

That is unfortunately to a bug, but a feature, see this link:

iPhoto and Aperture don't have edits to photos you import from iOS 8 devices

Apple is developing iCloud Photo Library Beta. It will be released next year for Macs as well.  If you enable iCloud Photo Library Beta, available in iOS 8.1, you can download the edited photos with the filters applied from your iCloud home page, when you open the Photos.app on the page:  https://www.icloud.com/