For example would you be able to change the language settings for typing foreign languages or change the background picture, and download all the apps you want?
And make it not play an Advertisement for the phone when it’s idle?
I found this comment about demo phones:
"A demo phone is heavily restricted. Usually with the OEM’s admin demo app, and the Store’s Demo app. It’ll be also typically chained to a deck with a special alarm that’ll buzz off if you try to remove the charging cable or cut it.
Some stores will render a demo device absolutely a brick if you do manage to silence the alarm somehow. It will COMPLETELY STOP WORKING, and no restoration software will revive it unless given back to the store it was taken from."
This seems to suggest that you can only use demo apps with a demo phone?