There are three welcome offers rather than one, and which you get depends on which product you fund first, not on which code you enter.
The casino welcome bonus is 100 free spins with no wagering requirement published against them. That last part is worth pausing on: a no-wagering spin produces a balance you can withdraw, which is a materially different product from a four-figure match carrying a 35x multiple. It is also why the headline looks small next to competitors advertising thousands.
The sportsbook welcome bonus is a 50% match up to $250, paid in free bets. The poker welcome bonus is 100% up to $1,000, released against rake. Neither is interchangeable with the casino offer, and you do not get all three.
A BetOnline sign up bonus and a BetOnline deposit bonus are the same thing described from two directions: the offer is triggered by the first deposit and attached at sign-up. BetOnline promotions beyond the welcome stage — a BetOnline reload bonus, the daily rebate, the leaderboards — are opted into inside the account rather than claimed with a code.
A BetOnline new user promo and a BetOnline first deposit bonus are the welcome offer under two more names. There is one welcome offer per product, it triggers on the first deposit, and no amount of renaming adds a fourth.