You should add a custom shortcut so people can spawn a part with a shortcut instead of having to click on the plugin and pressing the spawn part button.
That’s not how they work, essentially, you want to use Plugin Actions these are shortcuts that you set in your plugin script that the user can then assign a keybind to in settings. You, as the plugin creator, are not able to change what the keybind is, but its helpful for it to be there for people to use.
No you don’t, the user sets them them self. I’d recommend putting some sort of prompt in your plugin so that people know that there is one and how to set it.