An inspection usually comes in stages...the rough-in to verify the drain and supply lines are installed properly, then often a flood test, to verify that the shower pan is installed properly, and sometimes a third after everything is finished (not all places do this one). To get a proper inspection starts with pulling a building permit, and if done now, the whole thing might have to be torn out since the rough-in isn't visible to be checked.
See what one of the pros has to say that deals with this, but a true pro would have taken the time to pull a permit, get the inspections, and do it right the first time to prevent this from happening in the first place. Because the work was started without a permit, there could be a fine as well...the building permit people are part of city hall, but exactly where their offices are, you'd have to check.
A trap cannot be shared with other fixtures in the bathroom. And, to prevent accumulations of soap scum, hair, skin flakes, and who knows what in a long trap arm (the pipe going to the trap), it is best to have the trap immediately below the drain opening in the shower which keeps that trap arm short. That vertical pipe self cleans better than one turning and going a distance horizontally, too.