It comes with the GFCI breaker, Neutral and ground bar. There is also a bonding strap, that will not be used , assuming you are installing this unit in a sub panel application from your main panel. The bonding strap would only be used in a service entrance application.
It is understood that the neutral from the service will be brought to this unit with the power wires. Anything less would defeat the purpose of the breaker and its resultant safety.
It doesn't help that the 360 view doesn't show the back of the enclosure, nor is there any links showing the product details. Square D, Siemens, Eaton and GE all have knockouts in the back and sides of their enclosure. Midwest is the only one I can find that does not offer a rear knockout opening. I do not believe there is anything in the manufacturers directions that says you can or cannot make a conduit entry in the back of the enclosure, nor do I see a code requirement disallowing it , as long as wire bending rules are honored , the conduit opening is not made above live parts, and it is sealed with a gasketed locknut or other approved means. Nevertheless, it might be best just to go ahead and use one of the other manufactures enclosures that already have the knockouts, then there will be no issues.
The GFCI breaker will not reset if it has no power to it.
No, it will still function as intended.
In order for the test button to work, standard 240-volt power needs to be available to the pick-up jaws of the breaker. If you have these conditions when the test button is pushed the breaker should always trip. Power to the load side of the breaker should be interrupted. If it doesn't something is wrong with the breaker. Take it out of service.
This disconnect could work however it is a good deal more expensive than other items that would work better. A heat pump does not need GFI protection. The GFI breaker in this unit is what makes it expensive. A simple fusible pull-out disconnect is what is typically used for a Heat pump unit. What the heat pump could benefit from is the fused protection.
That nomenclature you are referring to (if you have accurately captured it) is obviously an error. I suspect the poor transcription happened in the transition between the manufacturer's specification and the Home Depot web site. This unit is rated at 50-Amps; a typical rated load of the modern hot tub.
Yes, The NEC requires the neutral to be bonded to ground in the main service panel only. However, do not use the bonding strap in sub panel applications, such as this one. When installed as a sub panel - put the sub feed neutral (white) conductor in the neutral bar, and the ground conductor(s) in the separate ground bar. The conductors going to the spa will all terminate in the GFCI breaker (red, white and Black) in their designated terminations, and the white pigtail from the GFCI will terminate in the neutral bar, with the neutral sub feed conductor.
It has a hole in the top.