iCloud backup download

How do I know when my backup has completed downloading? How do I know the progress of my iCloud backup download? What would be the average time for a backup downloading from the iCloud that I'd about two gigabytes in size? My phone asked me if I want to continue downloading my backup or so I want to delete? App data and backup will be deleted but I'm not come tell clear on what that means? Music is already backed up on iTunes so why is it seemingly part of my back up on the iCloud? I've been downloading my back up for a week now because I only have wifi at work and everything seems to be downloaded except music but iTunes likes to hide my music sometimes and I fear it may delete my music from my iTunes account if I delete my back up but everything else seems to have downloaded except for my vast array of music from iTunes which won't let me download new songs or certain songs. It will download songs then remove them. Lease someone answer this question!