You can lie on either side, but starting in second trimester, you shouldn't lie on your back because it causes an occlusion in one of the main blood vessels that supplies blood to your baby. He won't be deformed though. No harm has been done. You should just make an effort to not lie on your back in the future.
Laying on the left side is recommended so the baby gets good blood flow and is off your nerves. Laying on your backs isnt good for your organs when the baby reaches a certain weight. But intimately lay however is most confortable.
Sleeping on your left side is just to keep baby off of the nerves in your body is what I've been told. I've never heard that they might be deformed if you didn't.
Yes. It doesn't matter how you lay. You'll know when a position doesn't work. If it doesn't hurt, you're fine!