Nopke's mod stops the WANT to go to college, but it doesn't (?) stop them ageing up and crying because they didn't go to college..which is what really bothered me.
As for the "try it a see" hahah no

there have been a few times that I've wished that when you had a teen runaway it put them in their own household in the sim bin .. if you exited the lot and didn't bring them home .. though maybe get a message askin first what to do with them.. for them to "stay" on the lost, but can still be ran away .. or "leave" in which they'd get their own household

If it was your only playable sim at the time, it might work like death? My vampire sim got killed on a community lot by being poked by an angel (You know how it is!), and they were my only playable, I basically ended up left in edit lot mode, with the only option to be go back to neighbourhood (without saving).

I didn't save and my vamp was back home, upon entering their lot they just did the usual return home thing.

It's part of Squinge's pack here. http://www.insimenator.org/index.php?topic=96190.0

I get this glitch sometimes, not sure what causes it but I do know that the Butler making a phone call fixes it. In the scenario I experience, the house phone stops working and, like you describe, sims pick up the phone to make a call, but immediately place it back down, never completing the interaction. But cell phones usually still work; it's just an issue with the house phone. What fixes it is the Butler using the phone to fire other service sims.

So if you don't have a cell phone, you'd get one to call all the service sims. (You can get one through cheats, etc.) Then make sure you have hired the maid or gardener. Next hire the Butler and when he comes over, say yes, he can fire the other aims. He makes the call with the house phone and bam, the phone is working again. Fire him and get things back to normal.

Again, don't ask me why this happens or why this works (I swear I'm not crazy ); the thread where I learned this trick is lost to my memory. But it does work, so you could give it a try and see if it's the same glitch.

...Although I'm wondering if using the batbox to delete off-world loiterers would work, too. Idk, but I feel like this glitch happens when you save and exit with a sim on the phone, though I could be wrong.

What happens if a sim wears something that gets hidden by hider after being created?

Then they wear it.

Thank youu, I was worried about floating heads or something like that.

It's only hidden from you seeing it in catalogue. So its less cluttered, its not gone from the game.

Is it possible for a teen/elder career to have more then 3 levels?

I'm not 100% sure, but I think the answer is no. I think that is one of those things that's hard coded.

Yeah, I was wondering if it was hard-coded or whether it was just something Maxis did.