How to run (not only install) an android application using .apk file?

Question

Is there any command on cmd.exe that would allow me to start the main activity of a particular android application using the .apk file of that appl

Answer 1

When you start the app from the GUI, adb logcat might show you the corresponding action/category/component:

$ adb logcat
[...]
I/ActivityManager( 1607): START {act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10200000 cmp=com.android.browser/.BrowserActivity} from pid 1792
[...]