Questions about Nikon Mc-Dc2

No idea - ask a professional

Actually, no. With the remote shutter release you can only stop recording. To start shooting you have to press the button on the camera.

None is occupied.

Ja, das passt auch zur D7200 laut Herstellerseite: https://www.nikon.ch/de_CH/product/accessories/slr/slr-connectivity/remote-control/remote-cord-mc-dc2#related-products

I use the cable with the D5100, works fine. Built for D3100, it should work for D3400 as well.

Hello adibieri. No, the D500 does not have a corresponding connection. The Nikon MC-36 cable release would fit, but it is much more expensive and includes a timer. There may be other makes or manufacturers - but I don't know about them.

As an alternative, there would still be the Nikon ML-L3, infrared remote control for Fr. 38.90, which according to the manufacturer's specifications reaches up to 5 m, available at digitec, link: Nikon ML-L3, infrared remote control

Ja - 90cm ☺

Yes, it does according to the product page at Nikon -> http://www.nikonusa.com/en/nikon-products/product/remote-cords/mc-dc2-remote-release-cord-(1-meter).html#tab-ProductDetail-ProductTabs-CompatibleWith

Should fit. D3100 and D3200 are not really different.

No, unfortunately not. As far as I know, there is no wired remote control for the P900, only infrared or wireless. However, I can recommend the Nikon ML-L3, Infrared Remote Control which works great with the P900.

Yes, I also have a D750 and it works perfectly.

Unfortunately this remote control is not compatible with the Nikon Coolpix S3600.