It would mean the twelve year old has a cartilage piercing, nothing mystical about it, it's just a piercing.
You would have a bubble on your three year old lip piercing if the piercing is damaged or infected. The piercing can become infected if the jewelry does not fit correctly.
If the 12 year old has had the piercing for over a year, chances are good it's healed. If it was done by a piercing gun, then it could still be healing.
No
Regardless of parental consent a lot of piercing studios won't do lip piercing on a 13 year old. Body piercing studios generally won't touch anyone that young, but you could check with your local studios by giving them a phone call and asking.
If the piercing is over a year old you can remove the Monroe piercing for several hours without fear of the piercing healing closed. Prior to a year you are taking a gamble on how your body will respond to the jewellery being out of the piercing.
honestly no
You might have a bubble on your three year old lip piercing because the piercing might have been damaged when you exchanged the tongue bar or ring. You might also have a bubble because the tongue is infected.
no
10 year old boys should be 10 year old boys, out in the dirt and mud doing what young boys do. The ear piercing can wait till he is in his teens and can decide if he really wants his ear done or not. At 10 there are other more pressing issues he needs to do and ear piercing isn't one of them. I don't think it is right for a 10 year boy to get his ears pierced. They are way to young and when they're older they won't want it at all. They will regret it once they already have it done.
The one that wants shut down the quickest.
It depends on the shop and which piercing, call up or e-mail your local shop and ask :]