ANISTON Sears Craftsman 1 Button Garage Door Opener Remote Transmitter TX2028 315mhz

How do you change the battery? I followed program directions to a T, have successfully pored anothe purple learn remote to opener but this one won’t

Which replacement battery does this use? Both remotes did not come with batteries or instructions.

Is it waterproof?

will this work with Craftsman 139.55918 opener? I don't remember a purple button on it. Thanks!