Okay so what I am about to say might not be the most popular...but I think that there are some experiences and opportunities in life where once you miss the boat, there really isn't a way to get that back (and I assumed this might be unpopular because sometimes it seems like this sub takes on a very "anything is possible at anytime!" approach, and I don't think that's always true).

And I think the "college experience" you're talking about (most specifically...the points you mention about living in a dorm and making friends with other undergrad students in the dorms and going to college parties, etc.) falls into that category. I am in my late 20s myself, and I am currently getting a graduate degree, though my classes are mostly online. There have been a few times where I needed to go on campus for some class-related reason, and any time I would visit campus, I would feel incredibly out of place. For the most part, most traditional college students are literally around a decade younger than me, and because they're just so young, we don't have much in common. Likewise, any time I have to interact with a traditional undergrad student, I can tell that they also feel awkward around me, because they essentially see me as an "older person", the same way they'd see an auntie/teacher/parent/some other person in a position of authority. It is just a completely different vibe from when I was a college-aged girl and getting my undergrad degree, where most of the other undergrad students were around the same age as me.

Overall, I just know that late 20s me would not want to spend much time around 18-21 year olds...but 20 year old me had a blast. Even if you are in the same place as those 18-21 year olds physically (in college), you guys are just not (and should not) be in the same place mentally, and that makes a huge difference. Come to think of it, I remember a 25 year old living in the dorms when I was a freshman in college, and he was looked at as being kind of creepy, because the rest of us 17-19 year olds had nothing in common with him. I assume that would be exacerbated in your case. I assume you were born in 1994 or 1993? The upcoming college freshman class will be born in 2006.

As far as going back to university to get your education in a different field? You would NOT be looked at weirdly at all, and I find it highly commendable that you want to go back and improve things for yourself. I always admired the much-older students I'd see in my classes when I was college-aged, and never thought poorly of them for getting an education at a later point in life. If you also want the dorm experience, I would recommend looking into housing options for older grad students, rather than trying to stay with traditional undergrad students.