can bands on different labels play together? or labels wont allow it and just stick to label mates

Headliners can generally pick anyone they want to open for them. Many will hand-pick the acts they particularly like, want to help out, or think would be a good fit for their audience.

But if they're not the kind of artist that cares one way or the other, the agent or manager may very well pick one of their up and coming acts to be the opener. The headliner's label would probably like to use the opportunity to expose one of their new acts. That does happen.

I've also heard there is payola happening on some of the larger tours, like bands used to have to pay money to get on the Ozzfest side stage.

i was fantasizing about a living colour/3rd eye girl show