I've never played this game but reading rules here it seems clear enough. The rules say (emphasis mine)
In order to place tiles on the table, each player must make an initial
play of at least 30 points in one or more sets.
These points must come from the tiles on the player's rack and not
from tiles already played on the table. A tile is worth its face
value. A Joker may be used for any tile and its point value is that of
the tile it represents. The penalty for holding a Joker if another
player wins the round is 30 points. If a player cannot enter the
round, or purposely chooses not to, the player must take a tile from
the pouch and the turn ends.
After players have made their initial plays, they can also build on
other sets on the table with tiles from their racks.
so 1) No you are not allowed to play other tiles the same turn. The rules are clear that you must use your own tiles and not other players. It isn't until after all players have made an initial meld or passed you may start building off other players.
The rules for jokers state
A joker can be retrieved from a set on the table by a player who can replace it during his turn with a tile of the same numerical value and color it represents. The tile used to replace the Joker must come from a player's rack and not from the table.
So you can't reuse the joker since the 10 Blue was not in your hand.