Default Curious about Google Play Music...

So here's the thing. I don't have unlimited data, and thus, I can't just stream my music all the time, or I'll burn through my data allotment pretty quickly. I've always been fond of Play Music's save to device feature. There are some things I'm a bit confused by, though, and I'm hoping someone can clear them up for me.

For one, within the Play Music app, can you delete "saved to device" songs off of your device without deleting them from your Play Music library completely? Is there any specific way to do that?

Secondly, I'm interested in signing up for All Access, but similarly, I wonder how the offline functionality works for that, like with the radio stations, for example. It appears you can save the "custom radio stations" to your phone for offline play, but how many songs does it actually download? Aren't those stations supposed to just kind of go infinitely, until you stop listening to them? Does it only download a set number of songs (or length of music), or something? And how easy is it to delete these saved radio stations (and the songs from them) from your phone?

Sorry if any of these are dumb questions. Just never really played around with this stuff before, so I really don't know how it works at all.