A. If a build doesn't seem to include all the changes you made, go Lazarus IDE > Run > Clean up and Build ... and after that, do another Build APK and run.
B. To be sure the phone is running the latest build, I do this:
1. Have the phone screen always on when connected to USB.
2. I leave the previous version of the app running on the phone. I can see it on the phone's display.
3. I go Ctrl-F1 on Lazarus (that's Build APK and run on Windows).
4. I keep my eyes on the phone. When Lazarus finishes building the APK, and prepares to install the new version on the phone, the app on the phone will disappear for a second. (It is terminated by Lazarus via adb). And then it will appear again, when the latest version has been installed and started.
Therefore, if I see the app disappearing and reappearing, I'm sure that I have the latest version running. And if some changes I made is not appearing, I try Clean up and build, I double check my code, to see if I forgot something, etc.
In your specific case, if the app on the phone disappears and reappears, and it doesn't show the changes you made, the problem must be in your code or in some files being cached too much (so Clean up and build)