Questions about excluded tenancy

Other

Hi, I'm a new resident landlord and I've got few questions. Me and my wife have got 3 bedroom house, we rent out one bedroom to one person. We're going to rent out one more bedroom to a different person:

1. Is it gonna be HMO? Do we need a license to do it?

2. What kind of electricity centrificates is needed?

3. I've got a gym in my shed, I don't mind the tenants using it, how do I specify using it in the agreement? I don't want to take any responsibility if an accicdent happen.

4. We are using RLA resident landlord excluded tenancy agreement (room only), do I have to use a rent book by law?