Yup and yup!
Betas are aggressive fish, and should be kept alone. Some may be able to be kept with other fish, but most cannot. Betas have a labyrinth organ, which enables them to breathe air when the water is depleted.
The molly is a live bearer. They come in all colors shapes and sizes. You can tell the sex of a molly ( or any livebearer) by its anal fin. If it is pointed like a pencil, its male, but if its fanned out like a well, a fan, then its female. (live bearers give birth to live and swimming fry. )
Next! ( FW