How to detect the name of my current launcher?
Open Settings->Applications->default applications.
Tap home screen and select your required launcher.
(if you have only stock launcher(for Samsung devices, it will be Samsung Experience Home), then there will be only one present, if you've installed other launchers like Nova etc. , then there will have a list of launchers available. Selecting any one launcher will set it as default launcher of device)

As AndrewT said: When you install 3rd-party launchers(from play store or using apk), you just add more selections for the launcher, but not necessarily replacing it wholly. Or in other words, you can have 10 launchers installed on the same phone at the same time, but only 1 active launcher.