I updated to Google Play Services 6.5 and I want to revert back to actual official version I found the latest 6.5 release for the Google Play Services here. I installed it hoping the smart lock position feature would work and sadly it does not.

Since it was the only one for Lollipop I thought it was the right one for my Nexus 9, but I was wrong.

The app crashes every now and then, and it's quite annoying. Is there a way I can re-install/revert to the actual official version (6.1) without resetting the tablet? When I try to "uninstall updates" under the Google Play Services details it asks me if I really want to reset to default factory settings, which I only want to do if there's nothing else I can do.

When I browse to Google Play Services on the Play Store from my computer (since for some unknown reason this page cannot be accessed from my device, it says my devices (cellphone and tablet) both have the app installed... but my tablet still has the wrong version.
If you open Settings > Apps > find Google Play Services and select uninstall updates, that should revert to your previous version of GPS.

I think you did the same as me, as it wasn't clear on any site that this APK wasn't suitable for the Nexus 9 - were you getting an error message with regards to GP Music as well?

AC