Is it possible to create a program that applies XMP files to photos programmatically using Lightroom

"Is it possible to create a program that applies XMP files to photos programmatically using Lightroom Classic SDK?"

Yes. An outline of the steps:

1. Use LrXML to parse the XMP file.

2. Extract from the parse tree the develop settings to be changed and store them in a Lua table, as described by LrPhoto photo:getDevleopSettings().

3. Import the photo(s) to be changed into the current catalog using LrCatalog catalog:addPhoto().

4. Apply the develop settings from step 2 to the photos using photo:applyDevelopSettings().

5. Export the photos to your desired format using LrExportSession.

There are a lot of details left unstated here, of course. And there's a steep learning curve to learning Lua and the SDK, unfortunately.

Visual changes are down via Metadata with Lightroom. If you want permanent changes without metadata, you need to use Photoshop. 

If you're just looking for an edited look with all faders zero'd, then create a profile using settings via Camera Raw and apply a profile. 

I've made a few plugins, but not applying settings, but most that I've seen show a history step. 

What's your reasoning with not changing XMP?