Apply Image can be found in Image -> Apply Image
Duplicate is found in Image -> Duplicate
There isn't a hotkey for it so on my Photoshop, I hotkey them to F10 (Duplicate) and F11 (Apply Image). I usually use those hotkeys when I do my work since I like to use functions that apply to my entire work :>
Also that's a pretty nice sig
I think you have the idea of some of the functions. If you want a little critique though, the left side of the sig is a little too bright as in my eyes wants to shift to the left a little. I would apply another Level map and erase it accordingly.
I'll make/find more sig tutorials if anyone else would like to learn some more tricks :> There's other things like, using flow, color schemes/wheel, using C4D, text, using the pen tool, smudge brushing etc. if anyone else is interested