Is the battery in the helicopter removable?

the battery is internal battery, so it is better not to remove it.

Can you buy another charger for the tf1001?

You charge with any regular mini USB charger. Batteries needed for remote.

If I buy 2 drones will they have separate frequencies? whether will be interference both sets of remotes and drones.

The type of signal used by the transmitters, 2.4 ghz, ensures there will be no interference.

Can I fly this outside?

better to fly indoor and It can totally fly outside under windless weather

how to contact you if i have some issues?

pls send a message or a call for us. we will try our best to solve your issue. thanks