There are people who can sense other mediums without even talking to them, I've known quite a few and I am one myself. Perhaps it 'comes with the territory'. A true psychic would be able to tell as well so it's plausible enough. If you're still in contact with them then it's worth thinking about asking their advice as to next steps, I'd guess that if they can't help you themselves they may be able to point you in the right direction. Really the only answer to this is to try and and experience it for yourself.

Most good mediumship development people are nurturing and they'll lead you by your metaphorical hand through your development. I'm guessing that the reason you asked that question is that you're curious enough to want to pursue it but there's a part of you that's wary. And your mind has probably conjured up some scary stories to tell yourself. Mediumship circles are protected and their leaders are always keeping an eye on you, and they would pick up an anything suspicious straight away.

If you don't at least try it, you'll always be wondering and there's nothing worse than sitting there in two month's time thinking "What if I had followed that through?".

It's not really a case of being more or less advanced than the other, it's just different. Psychics read people directly but that's a skill in itself, so depending on the psychic they could be reading energies, facial micro-expressions, body language, using their intuition, watching reactions..... Mediums make a direct Spirit link so it's a communication with Spirit on a one-to-one basis. Keeping it very simple for the sake of clarity. Both have their own power/talents. Some put mediumship above being psychic and others put the 'clairs' into hierarchies but really, it's snobbery.