@R0M: To enable Gallery Labs, head to the Gallery app > Tap the 3 lines in the bottom right > Settings > About Gallery > Repeatedly tap on the version number until it says 'Gallery Labs enabled'. If you then head back into the Gallery settings menu, Gallery Labs can be found towards the bottom of the list. I hope this helps.
@R0M: From what I understand, if there is a number to the right of the 'Gallery Labs enabled' notification e.g. Gallery Labs enabled -2, then you'll need to tap the version number until the number disappears (so, in the case of my example, 2 more times). Let me know if this works for you.