My ultrasound tech asked me if i was sure about my date of conception bc she said I was 2 weeks and 6 days farther than I thought. They will definitely know, maybe you should ask next time(:
No that's super rare, they base their age guesses on development of the fetus. At 8 weeks your baby is like a little worm with nubs, by 12 weeks they would have developed their limbs already, so its quite a big mix up
The ultrasound will tell them its weird but true
The ultrasound will tell you the accurate time I thought Iwas 17weeks but nope actually was 16weeks they are gonna go by the ultrasound