Integrated rear carrier battery

I have a Schwinn ascension walmart model, not the target one, has a funky collar so space is a problem i believe for a regular battery - that being the case I am looking at the 52V rear carrier.

my question is (due to lack of explanation on the page) does the battery has removal capability?

- like if I go into a store, can I slide the battery out and bring with me?

also — is that a brake light? Is it light sensitive, meaning auto on and off or manual? Or does it have braking sensors installed?

thanks.. (maybe add a video showing benefits or non benefits of this mounting system?)