Can I use parts from my 2001 Honda Civic lx on a 2001 Honda Civic ex?

Can I use parts from my 2001 Honda Civic lx on a 2001 Honda Civic ex?

Yes, if they are compatible.

Yes

Most of them, yes. Obviously there are differences between the two trims. In particular, the audio components are not compatible. I'm pretty sure 2001 was one of the years Honda built the security and unlocking system into the EX radio.

Yes.

You don't need my permission

Probably. Car makers use a lot of common parts in order to keep costs down. Your two Hondas are probably identical under the skin, apart from minor trim differences. Check they both have the same engine though, if that's what you need.

Yes, but mechanically, they different engines. The EX has VTEC whereas the LX does not. The wiring is different as well as the ECU programming. Everything else is interchangeable.