Yes you can but by the time you’re 30 weeks or so it’s not recommended
Yes, I worked in OB and all the doctors I worked with were like "sleep however you freakin can" for me that was my stomach in the beginning and then my back, I had twins and as they got bigger if I laid on my left side I'd squish my daughter and she'd start kicking and freaking out until I rolled over and then on my right side I'd squish my son and he'd freak out and kick me til I rolled over so my back it was!
Update: I slept so good after getting on my back 😂😂. Passed out almost immediately
Best way I used is a couple extra pillows just to prop my head up
Technically yes. They recommend you only sleep on your side but during the first trimester it’s not as serious.