You CAN stop taking the folic acid, but you can also keep taking it. It's upto you. I'm still taking my prenatal vitamins, mainly cause I've still got them, so might aswell take them. But also cause of the other vitamins that come with it I guess. I stopped taking them at 12 weeks when I was pregnant with my son though, mainly cause they were huge and I was really bad at taking pills at the time.
And after my scan I got a sheet of paper with all the info on it, that's supposed to go in your pregnancy notes. It said the size of the baby and NT measurement and also what my duedate was and what else was seen on the scan (she checked the heartbeat and stomach and brain etc. - All appeared normal, ofcourse that's all gonna be reviewed at the 20 week scan).
And if you opt for the blood test aswell, then you should get your results in a letter sometime after your scan. I was told I'd get a phonecall within 3 working days if something was wrong or if I was high risk, so in this case no news is good news! Haven't received the results of the test yet though. I think that can take a while for them to be sent through (it's been about 10 days for me so far)
Good luck!!