I’ve not tried this, but the Mendix SDK exposes an interface you can use to query your applications.
In the Module class there is a fromAppStore attribute. The App Store was renamed to Marketplace a while back. You could try looking at this and seeing if a true value has been set. If it has, it’s come from the Marketplace.
Hope this helps, and if it works, please do let us know.
No not that I'm aware of.
Besides opening the local project folder and check if there are Java folders for marketplace modules and in widget folder if there are non standard widgets.…
But in that case it's easier to check it in Studio Pro