Either. You can set it to auto show the pictures or they can sit in the inbox until you approve them. You can also set up whitelisting for email addresses to only accept pictures from them or you can block certain email addresses.
yes, the frame has its own email address -- you simply mail the photo to that address and it can automatically be displayed -- you also have the option to "confirm" before showing a picture on the frame --
As far as I can tell once you givethe email address to someone if they send you a picture to address it will automatically be uploaded. If you don't want to picture on there you would need to manually delete it.