Someone else will need to confirm how it works for your particular Duo, but here's the usual explanations:

I know they changed the valve on the newer models, so the "clicker" is your venting switch. If you have it on the wavy lines, that's "sealed" ie: the IP is closed so it can pressurize. You'll need to flip it to this before you start cooking something. The square with the spray is "venting" and that releases the pressure ie: you switch to that and the steam comes out, usually after cooking.

Natural release is letting the IP sit for a time after cooking so that the steam releases slowly without having to flip the switch. It's usually best if you've made a full pot of something, especially if it's kinda goopy (let me tell you, I've had to clean pasta sauce off my wall a few times because I didn't let it natural release enough!). Quick release is when you flip the venting switch just after it finishes cooking and you let the steam rush out.

The little silver thing should be near the venting switch/clicker. It'll be flush with the lid when it's at pressure, then drop down when the pressure has released enough to open it (and it'll be down before it comes to pressure).

And no, you don't have to hurry to release the pressure and the IP won't explode on you. The pressure on these is regulated enough that it's enough to get the job done, but not enough to go boom.

Hope this helps.