1. Ruth Doctor was The Doctor with no sonic. 5th didn't really use one after his first got destroyed, 6th sorta kinda didnt. But 6th would be the only one I can see claiming to be smart enough to not use one. Though that stuff could be irrelevant.
2. Jack could have been using a Gallifreyan ship, which is why it had an active time scoop.
3. Ruth's TARDIS control room was damn near using the default desktop theme.
4. There's no way for any gallifreyan or time lord to not know Gallifrey was destroyed. Gallifrey is time locked. You can't travel to or from it's past or future.
5. I wanna say Jack couldn't locate The Doctor not because of the Judoon force field, but because it wasn't HIS Doctor.... but wouldn't The Sonic pick up that Ruth wasn't the same Doctor? I would think the TARDIS would pitch a fit if an alternate universe Doctor was casually chilling inside her.
6. But at the same time, at least we can say they aren't the same regeneration number. Remember the cloister bell ringing when there were two Capaldis (one in the coffin thingie, one running around that undersea base)
So, uhh.... alternate universe? Maybe MetaCrisis Doctor found a way to regenerate and they're really in Pete's World? But that wouldn't make sense either. Actually it kinda would?
Why would a Pre-Hartnell Doctor even have a Police Box though? Memory wipe?
And if they ARE in another universe, when did it happen!?
what if they're on some Brain of Morbius type shyt (@18:00 - 18:55), where The Doctor had memories of incarnations Pre-Hartnell buried in his mind?
What if it's Looms?