There are a lot of different species which serve as pollinators besides bees. Afaik, some are more specialised into specific flowers/plants than others and without them, these plants wouldn't be able to reproduce. (Yucca moths for example.)

If the female wasp crawls into the caprifig, she can successfully lay her eggs and die. The males hatch first, mate with the females, dig tunnels out of the caprifig, and die. The females, now covered in fig pollen from the caprifig, fly out to begin the cycle again. If the female wasp crawls into a female fig, she will not be able to successfully lay her eggs despite pollinating the fig with pollen from the caprifig she hatched in. The fig will absorb her body and her eggs as the fruit develops.

https://en.wikipedia.org/wiki/Reproductive_coevolution_in_Ficus

Yes, they are! They're into sweet nectar - that's why they also tend to visit our sweet drinks. The adults also sometimes search for bits of meat for the carnivorous larvae. In this mode they act like insect pest control.

Yeah. They usually pollinate my sweet toast in spring and my ham in late summer.