You can get the 4d between 28-32 weeks. Other than that, it just depends on your dr and your health insurance but you likely won't have another unless something is wrong.
Yes I guess! U shuld have another 1@week 35.
Depends on your age and high risk. If not then no.
You might have to go somewhere else to get anymore
With my daughter I didn't have any ultra sounds after they resolved the issue with my 20 week one.
I had another one at about 38 weeks with my first. They wanted an estimate on his size.