I have a few questions regarding this lot type:
1)How much do they differ from dormitories? Does the latter are rendered useless in the overworld?
2)How effective are they without the LN and its system?
3)Are hidden makers requirement or are they not?

(If you got a question or just want to discuss it, you can do so here without having to start your own).

1) The Apartment lot type from the University Life EP will turn a regular residental lot into a dorm type apartment as you can find them in the University world. Other residents move in until 8 sims (including your household) live on this lot, but those cannot be controlled by you. Dormitories in the Uni world are in fact residential lots with the University Apartment lot type.

2) They work exactly the same in home worlds and in university worlds.

3) This is not the same as the Late Night Apartment! They are entirely independent of Late Night and do not require anything from that EP. As such, they don't require any room markers.

If interested there is an apartment mod:
http://modthesims.info/d/498857/ts3...-1-63-1-67.html

Is it because the other sims get attached to your household? Had that happen to me once.

I had that once where I placed a Sim in a one bedroom apt and I think next time I opened the game she had 6 roommates all of the sudden. Took me a minute or 2 to figure what the heck was going on.

Yes, better avoid the apt lot type. I had to struggle a lot to revert it back to something else. I tested a mod that used the lot type. I don't know if he/she managed to fix the bug as well.

I think I also had routing errors with sims trying to come to or leave the lot?