Is it possible to not have the play store locked but have the action of installing an app locked?
I don't believe so im afraid! Its either allow Play store or not. Im sure things could well change in the future!
But on another note if you dont want any users installing anything whats the point of allowing the play store?
You could use App control functionality tho - user will be able to install the app, but won't be able to launch it.
