We can go into recovery mode in android phones, which is usually home+volume up+power for samsung phones
This answer says that the recovery mode is like a simple OS that the device boots into. This OS then is not restricted by protections and folder permissions implemented by android, so it can see root folders and write to it if needed. I have also once seen (not sure of all the steps I did but I remember doing it) that a zip file in the sdcard root can be used to temporarily change this recovery screen software to something else (I think it was CWM recovery zip file, but it was the type where once you restarted the phone and went to recovery mode again, you would have to run the zip file again to get back to CWN recovery screen. There was a way to permanently replace the recovery screen with a CWM recovery but I didn't try it)
If that is the case, is there anything like a live CD for android? preferably also with a touch screen gui, and able to install and run apps from the phone's internal memory or sdcard? Has this been done or is it technically unfeasible? Would it have to be separately made for different phones?