Is it possible in the UML to model transition from an outer state to an sub-state of a composiste-state like in the following figure (State3->State1.2)?
If so what is the semantics?
I guess When event occurs in State3
- the State3 Exit Action is executed
- the State1 Entry Action is executed
- the State1.2 Entry Action is executed
am I right?

Yes, you can. From the superstructure: