I have a 9day old/new Samsung S8 (though this is probably a generic question).

As with most of the new Android phones I have owned I tend to install all sorts of new apps, realize they a buggy or useless then parse down to the reliable few that I have been using for the 8 years or so.

For the sake of argument let's blame the apps which seemed to result in excessive battery drain, an occasionally warmer (not fire-cracker hot) than normal charging cycle, and occasionally a screen that does not power off. But it is possible that the problem is the phone itself as I have been assured that these are not symptoms typical of a "normal" S8.

To my question (and not expecting definitive answers, just opinion)...

1- What are the odds that I have damaged the battery?

2- What are the odds that it is the phone not the apps?

As the issues has been intermittent, even removing the apps and running bare bones will not necessarily demonstrate that the issues are phone vs application based, add to that a rapidly closing 14day return window I need to make a decision very soon.