Q: iCloud - share - auto sync

You can set up automatic downloads of music, apps and books from your itunes and app store account. This can be done with all your apple devices.

go to settings/itunes and app stores/turn on automatic downloads

You can share your itunes library by setting up home share. This isn't through icloud but through your home wifi network.

Home sharing support

http://www.apple.com/support/homesharing/

Understanding Home Sharing

http://support.apple.com/kb/HT3819

You can also set up itunes match for a small yearly price and sync all your music from the icloud

iTunes Match

http://www.apple.com/itunes/itunes-match/

How to subscribe to iTunes match

http://support.apple.com/kb/HT4914