I looked at many other links and stackoverflow posts but nothing fixed my problem, I installed my app through android studio and I deleted it after I turned off developer mode, now when I try to install it from the google play store it tells me “You cannot install this app because another user has already installed an incompatible version on this device”, I tried to open the app list that shows the apps in alphabetical order but it wasn't there, I tried to access the app list from storage but the app wasn't there either. I tried to install it again from android studio (I turned developer mode on again) but the app wouldn't install, I got an error that says there's no MainActivity but I'm able to run the app through android studio on other devices.
What else can I do to completely delete the app from my phone and finally be able to download it from the Google Play Store?
You can use adb (android debug bridge). It's included with android studio SDK tools.
Just find your installation folder and run in cmd
adb shell pm list packages
This will list all the packages installed on your phone. If your package is listed then its installed. Then to uninstall it
adb shell pm uninstall YourPackageName
If there are any issues it will return an error.