you can trade with BAWSAQ, I think
just not the other one
nope, it hasn't opened yet in GTA online. tbh, it's probably because of people like blaze.
also wtf, you must have some playthings as you've likely accumulated 1mil+ from the cash card & mission grinding.
I can't recall if it was open or not when Online fully launched, but BAWSAQ was definitely online prior to that, when only singleplayer was available.
But at the time it was still connected to the multiplayer service, and players in singleplayer could use that stockmarket.
Reddit then got in on it and organised a big purchase of a single stock over several days to greatly increase it's price, with the plan to then sell it all off to make mega-money.
But the plan didn't work properly and they just kind of broke the stock system, and everything got stuck at the highest buy prices.
Rockstar haven't put it back in to the game since.