Possible to run at 90% of your potential starting up again at 25?

Try it and find out.

35 min for 10k sounds ambitious to me but that should not hold you back.

There is also the chance that you might want to increase your race distance to HM or Marathon in the future.

Keep on running.

No, you can only run at 87.5% of your potential at 35.

Now, for the serious answer: if you have it in you, you will run those times in 5-6 years at worst. If you don't, you'll run the best times that are possible for you in those next 5-6 years. Age will hardly be a factor around 30.

Yes, it's possible. My guess is that you'd hit it closer to 30 if you trained hard and consistently enough. But the question isn't whether it's possible. The question is whether you want to pay the cost, to get what you want.