How does the Snap! team decide which projects to put in official collections?

collections like:

I'm actually not sure. I think that you can add your own projects to some of those categories. Other than that, the team looks at recent projects as anyone else does, and will decide "this is a good example of that category."

The Featured collection is a little different; you can't add yourself to that one, for sure. :~) When we come across a project that has a really creative purpose, or has a beautiful graphical result, or has really elegant code, we'll put it in Featured.

is it possible to request projects to be added to the collections?

Sure. No promises.

could you add Block Flipper to the games category?

Games... not my department... I'll ask though.

A few months ago, a limit of 4 project pages was introduced, why?

Even when you search for projects with

return 4 pages !