Why does the inspector say this must lock open? It can’t be an emergency escape and rescue opening (commonly referred to as egress window), as it’s too high off the ground and not tall enough. Just curious what specific code issue he’s concerned about. Also, did the window open before tue ceiling was drywalled? If so, you might want to talk to whoever finished the basement, not the original builder. Also, if they used 1/4-in. drywall on your ceiling as you say, that’s highly unusual.