Does DOMS mean growth?
No, it means damage to the muscle. Proper recovery and nutrition leads to growth as a result of the stimilus.
Are DOMS required in order to make gains?
No. Proper recovery and nutrition leads to growth as a result of the stimilus. It depends on your level of preparedness. Novices can progress without much soreness, or work for that matter.
However, the more advanced you get, the more positive correlation to DOMS and Growth
If you DON'T feel DOMS after a training session, was that training session even effective?
Yes. Just because there wasn't soreness, doesn't mean the muscle wasn't worked.
If you DON'T feel DOMS after a training session, is that the cue to switch up your routine in order to hit the targeted muscle group at a different angle?
Not necessarily, but it is good to switch up exercises to keep from accomodating.
Is there a point where you should stop getting DOMS altogether?
When you die