Yes, as long as there is time left in player’s turn.

No

Yes, but the player must announce what the jokers represent ( example: 2, joker, joker – is it three 2’s or 2,3,4!)

Yes, or with any number of tiles; only a joker being retrieved from the table must be replaced with a tile from player’s rack and used immediately with two tiles form player’s rack to form a new set.

Yes and no, depending on the date of the instructions you are using. The earlier rules state you cannot, while later/current rules say it is legal to so (the change was made because the earlier version was thought to be too difficult for newer, less experience players). The method of play should be decided by all players prior to start of the game.

No, once the joker has been played the only way to use it again is to follow the printed rules. Even if you are not changing its color or number.

No, scoring is done at the end of the round using only the tiles remaining on your rack.