Mavericks said:

Question: why [Leia] didn't take an occasion to escape in the lifeboat together with the droids?

"There goes another one"

"Hold your fire. There are no life forms. It must have been short-circuited."

Better to choose a small chance of survival, even though it is tiny, than choose certain death in the escape pod.

At least one escape pod was jettisoned before... Maybe that one contained another droid with another copy of the Death Star plans. ;)

But then why they tried to kill Luke, Han, Leia & Chewy in the trash compactor turning on the ramming?

Not planned. The trash compactor is automatic.

I don't think that the imperial officers tracked the heroes escape into the trash compactor.

4. The explosion of DS II at the end of ROTJ.

This has been debated endlessly. Google "Endor holocaust".