What are the rules for objects garbage collection and motion between sims?

So I bought this nerf gun that rezes and shoots darts. The darts derez themselves after a few seconds so it's benign. But I have questions.

When does garbage collection occur on a sim?

Do all sims collect garbage at the same time?

Can an object not on my property avoid derez?

Between garbage collection, can an object run through multiple sims?

Trying to get a better grasp of my resources here. Feel free to fill in any gaps in my questions and include any gotcha info. I don't remember running across this information anywhere. Thank you.

Asking this almost evokes vivid imagery of the trash being hauled away!

I'm currently asking to find out more from an expert in this.