When you enter the STAR & the ILS for the airport of intended landing, the altitudes will appear on the LEGS page. That way if you get vectored off the STAR to let's say the outer marker or something in between, it not a problem. In the RW, the controller will issue altitudes with radar vectoring. Sometimes the altitudes could be different from the published ones depending on the traffic.

In any event most controllers are very aware of the normal capabilities of the plane they are controlling and it would be rare for them to give you an instruction you would be unable to comply with using normal flight maneuvers.

It is also very helpful to have a printed chart on your desk next to the joystick so you can grab information at a glance and it will help with your situational awareness of where you are in the approach. In real life we would never fly an approach without the paper chart in the holder next to us, and the runway diagram as well so you don't get lost on the ground.  ::)

End of lesson for the day...now go read some more!  ;D
Lou