How do I know which state’s health insurance laws apply to my health insurance?

Sorry if I picked the wrong flair. I want to get assessed for autism. Unfortunately, the insurance laws in the state in which my dad lives and works (I’m still on his insurance) and the state in which his insurance is based don’t require coverage for the diagnosis and treatment of autism in adults, so I’m assuming it isn’t covered. However, I live in a metropolitan area that’s split between two states, and the other state’s law requiring insurance to cover diagnosis and treatment of autism doesn’t say anything about an age limit. If I get my own health insurance through a job in that state, will that state’s laws apply, or does the insurance company have to be based in that state, or does the company I work for have to be based in that state? I definitely can’t afford this without insurance.

Edit: I’m 25. I make about $34k/year. (I still live with my dad but I plan to move out soon. I’m not sure how much he makes. Maybe $20/hour?) I don’t feel comfortable sharing my exact zip code (and I don’t think it’s relevant anyway), but I have posted things that imply which city I live in before, so I guess I’ll go ahead and say that I live in the Kansas City area, on the Kansas side. The other state is Missouri.