Question about eufy Video Doorbell E340

yes. You have to take the doorbell off the door with a push pin and then you charge it up like a phone using USB c. Demending on the settings of the doorbell you get a different battery length. I would say it ranges 3 months to 7 months. I charge mine every 6 months

Yes, you need to remove the bell from the wall and connect the battery.

Indeed yes - USB-C socket on the battery.

Yes