iTunes match in iPhone

I have doubts on how iTunes Match works really.

So lets say Match is enabled both on my itunes and iphone. I have a playlist "X". On my mac, I add a song "Y" to my playlist "X". This song is ripped from a CD. Itunes match is updated (how often does it get updated automatically?) and the song is matched and made available on my icloud.

Now, on my iphone.. is the Music app supposed to add the song Y to the playlist X automatically?

is the entry added but I have to download the song manually by playing it? how does it work?

what happens with songs and I have un-checked in itunes? are those not updated?

I had a bunch of un-checked songs, but I checked them again, updated itunes match, but they are not appearing at all on my iphone.

I'm confused!!

thanks.

(and happy new year)