It is rated for 250 volts / 60 amps. So as long as your heater is under those - yes it can.
No. Code requires the outlet to be on a separate circuit.
If your AC requires no more than 15 AMP, You can tell the GFCI is 15 Amp because the wide prong hole is not "T" shaped. 20 Amp outlets will have that one T shaped.
15 AMP, you can tell because the wide prong hole is not "T" shaped. 20 AMP outlets will have that one T shaped.
You can use this for a hot tub--with the code changes in the 2017 NEC, I think it'll be cheaper to use this in conjunction with a GFI breaker in the panel. This will allow you to run romex wiring to the disconnect. If you use a hot tub disconnect, you will need to run MC wire or run pvc and THHN wiring to it. What I'm waiting to find out is if this will satisfy the requirement for the Code required receptacle for the hot tub (you need one 6'-10' from inner wall of hot tub). If it does, then it's an even bigger savings. If not, you can use a cheaper disconnect without the GFI.
Probably not. The pool pump requires a GFCI circuit breaker for the 240 V circuit. This unit does not include a GFCI for the 240 V service - only for the 120 V service.
The pull-out device is not a fuse. It is simply a connector block. If you install it in one orientation, the connections are made. If you install it upside-down from that orientation, the connections are not made.
Only if you keep the cover closed and locked...
The AC disconnect is intended for a 240 V service. The GFCI is an auxiliary device, and will be 120 V. They are two separate circuits, in one box.