Er..timszta..
Your first two statements are saying the same thing.
The third needs to be qualified so that you only reduce V1 to equal VMCG when you need to and when a range of decision speeds is available that allows you to.
Your fourth statement is correct.
VMCG is most limiting when the asymetric thrust is high, that is at low altitudes, low humidities and low temperatures. You are most likely to be VMCG limited at light weights because V1 tends to be greater when you're heavy.