Yes, the Heckler & Koch Mounting Plate will include 2 X T20 steel Torx Plus screws for mounting the optic plate to your slide.
The holosun 507C and 508T use the RMR footprint so plate #2 should do you alright. the 509T actually ships with an adapter plate that is specific for it, and supposedly it mates the 509T and an rmr footprint. that being said, I dont know if the #2 would work for the 509T or not.
No, this Heckler & Koch Mounting Plate is designed for optic ready VP9 pistols. You would need a dovetail adapter like the Evolution Gun Works Leupold DeltaPoint Pro/RMR/Venom Sight Mount, found by using the link below:
https://www.opticsplanet.com/s/egw-p30
No, once the RMR Heckler & Koch Mounting Plate is mounting to the VP9 Optics Ready model the RMR can be mounted directly to the plate.
Yes, you would need the DeltaPoint model.
No it doesn’t. It is made for the VP9 optics ready which is factory cut for the optic plate.