Yes. Aulani and VGC are both DVC resorts and you can use your points at any DVC resort. What you can't do is trade into the hotels at DL (DLH, PP or GC).
As I read the info DVC cannot restrict usage at DVC resorts between retail and resale. Getting the reservation itself might be tricky for some options but this is true regardless.
Yep, we bought from the timeshare store at AK and stayed at aulani earlier this year. did not have an issue. since it is not our home resort, we had the 7-month rule.
Yes. Aulani and VGC are both DVC resorts and you can use your points at any DVC resort. What you can't do is trade into the hotels at DL (DLH, PP or GC).