No, you don't need to pair bluetooth to use it.
Ramo Art is designed for microsoft surface devices. here below is the full support deivices list:
Surface Pro 3
Surface Pro 4
Surface Pro 2017
Surface Pro Laptop
Surface Pro Book Series
No need to buy battery - it has a rechargeable battery built-in.
You had better not use it while this pen is charging.
Because the battery of the pen will be damaged.
No, it will not stick to the side of the surface.