Basketball players do it all the time. It is perfectly fine to do so.
However, if the finger is your fore-finger, it may be tough. Shooting, passing, and most other actions other than just defending involve the fore-finger.
I would wait until you are able to do things with it normally without feeling pain or discomfort, or if it is constricted with a bandage during physical activities.
This depends on how badly you have jammed it. Usually if you can still get movement out of you finger you caan immediately return to your sport but you may want to tape it or get a splint. If you...
It depends. Different teams make up different plays. If you observe basketball, you will see a teammate or two hold up a number. Suppose it's 2. That could mean that they do the 2nd play that they...