What happens when you restore an iPhone?

Does the iPhone lose my number? I want to back it up to a different back up time.

No. The number can't be lost through a restore.

No but if you've got new numbers you won't get those back. You will get the numbers from that backup so whatever numbers were saved during the time of your backup, you'lll get those back but say you added a number a day after you did the backup you won't have that when you restore.

When you restore an iPhone it will be like you just bought it from the carrier, the apps, calendar information, contacts, photos, etc will be erased off of your phone.