S.G.
1) If you're connect via iCloud, it should be backed up.
2) It should at the very least restore to the last sync - so you won't have lost everything.
3) Games, music, etc that you buy in the Apple Store will be restored or can be downloaded again. They will not be lost.
4) An iPhone hard drive is just like any other hard drive. Deleted doesn't always mean deleted. It's possible it's still there. You'll have to take it to a data recovery specialist and see what's possible. Sooner rather than later before you overwrite it. But be prepared to pay a lot. Like $500+