I haven't been able to fulfill these wishes either. The "meet someone online" is related to online dating, I think, but my sim has done that and it hasn't registered. And I've lit fireworks before but it doesn't really seem like an extravaganza, and doesn't fulfill the wish.
For the online dating just click on your Sim's computer. When the interactions pop up in my game I click on more (I think....I'd have to open my game to be sure) then click on online dating. You can choose make a profile, check messages or browse profiles.
My sims meet someone online got fulfilled when I accepted a request from one of her messages in the online dating (Connor Frio) then at the festival Connor Frio walked up to her and in the conor of the screen it says something like it was nice to meet you in person maybe we can go on a real date sometime. If you send accept a message from someone on online dating if that person sees your sim out the will automatically go up and talk to your sim.