1. Lots of things show up in Google activity if they're associated with your Google account in any way. com.osp.app.signin is related to the Samsung Account app, and so it would not be surprising if the Samsung Account app were intermittently accessing the web to refresh data related to your Google account. I'm not a Samsung nor Google engineer, so I can't tell you exactly what it's accessing -- but the point here is that this particular app is
not malicious spyware, and its presence is not a sign that a person has been hacked.
2. If you set up 2-step authentication for your Google account and you're not getting a 2 step authentication code via text (and you're not using the Google Authenticator app), then I'd be concerned that it wasn't set up correctly. Consider doing it again:
https://support.google.com/accounts/answer/185839?co=GENIE.Platform=Desktop&hl=en. Having sophisticated spyware installed onto your phone by a "hacker" is much less common than most people assume, since it takes a good amount of skill to do it without any trace. Finding searches on your Google account that don't belong to you could have a number of explanations -- one possibility would be if you logged into your Google account on a public terminal, and then forgot to log out. The next person who came along to use Google Search wouldn't necessarily know that you were still logged in, and therefore those searches would become part of your search history.
3. Are you saying that you actually have been a victim of identity theft? If so, have you brought this to the proper authorities? Or are you simply concerned that you're at risk for identity theft? Identity theft is certainly a big problem, but that doesn't happen because of an app like the one mentioned in this thread showing up in Google Activity. If I had no idea what that app was, I certainly wouldn't say it's nothing to worry about. But I was able to find that the app is related to the Samsung Account app, and therefore I did not feel that it was of concern.
4. We get a lot of posts on these forums from jealous significant others who snoop on their partners' phones, find something they don't recognize or understand in Google Activity, and jump to all sorts of wild and unhealthy conclusions. Apart from the fact that these people are invading another person's privacy (it doesn't matter if they're a significant other), it's also usually much ado about nothing. The OP of this thread was worried about the app in question having to do with a chat line, so it's pretty clear what their line of thinking was, and is why I responded the way I did.
I apologize that my remarks were upsetting to you, but they really were not directed at your specific situation.