go to the play store and search for instagram (you have to install it first of you uninstalled it) then instead of opening the app scroll down and, if you're in the beta test program, you should see a message that says so (i think its below the reviews or somewhere there), it'll give you the option to leave the program. After leaving it you uninstall the app and reinstall the normal one (just search for instagram).
hope that helps!
I've started to upload my images to lightroom and without editing just saving them from lightroom to the phone. This gets rid of the blurryness and pixalated edges that would otherwise be on instastory if uploading directly from the cameraroll.
I think it might have something to do with the format it saves it as?
Also tried to take a picture on snapchat and saving it localy and then upload from there to instastory, quicker and seems to work just as well.