I saw it in a review, so idk

Some models support it. I had one from PowerAdd

They are, kinda. You can buy a power bank that can be charged and still output energy

Depends on where you’re from, but I had good experiences with mailbox.org

Sure you can do that, but please backup your data before attempting the conversion, in case anything goes wrong

Why remove the address stickers? A person that has access to your garbage cans probably knows your address anyway