No, there is not enough rail space to mount this light on that pistol.
No, the H&K USP Compact does not have an accessory rail to attach this to.
No, there is no level 2 or level 3 holster that will accommodate this light mounted on a Glock 17. Duty holsters are made to be specific because if they are not then they lose some of the purpose of the active retention.
Unfortunately, the Olight PL MINI Valkyrie Rechargeable Cree LED 400 Lumens Pistol Light has been discontinued. I would recommend the Olight PL-MINI 2 Valkyrie Rechargeable LED Flashlight, found by using the link below:
https://www.opticsplanet.com/olight-pl-mini-2-valkyrie-rechargeable-led-flashlight.html
Yes, it will.
Yes, it will fit your P2000SK.
yes, it will fit your P320 XCarry.
Yes, this light will fit the P30 accessory rail.
Unfortunately, not at this time.
I do not believe it will be small enough. You will want to use the PL Mini 2 instead.