Generally speaking it’s not possible to strictly deduce code from its output.

But you can establish a pretty good guess by converting log messages into regexes then using those regexes in github code search.

You can look at some of the documentation to see how at least some of it works.

https://developers.google.com/google-ads/api/docs/start

And here’s Matomos analytics

https://matomo.org/guide/apis/

Is that what you’re looking for?

not sure what section you mean, but check out jadx: https://github.com/skylot/jadx

Experience in java is recommended.

Not sure, but https://exodus-privacy.eu.org/en/ lets you check any app for the presence of trackers. Is that relevant?