I wanted to get the install file (.xap file) for a certain purpose from an installed app on my phone. My phone is Nokia Lumis 625 running Windows 10.0.14393.693 and is interop-unlocked. Any way to get this done on my phone? Thanks.
For an interop-unlocked W10M device, the app you want is App Data Manager, available on the XDA-Developers forum.
Install (sideload) and launch it, go into Apps (may take a while to build the index), select the app you want to extract, and hit "Create archive from installation path". Select the location to save the created file.
Note that you may need to modify the contents of the archive a little bit (and change the extension to .xap or .appx, as appropriate) to get it back into a sideloadable state, if that's what you're going for. If you just want a look at the app's binaries or data files, though, that should be all you need to do.