As far as I know, J1 visa cannot be changed to H1 visa. The regulation might depend on the nationality of that person but in case of Nepal, what I said is true. You might be able to stay in US in TPS even after your J1 visa expires but you won't be able to work with EAD cause that will be violation of the J1 visa rule. I think same might apply to F2 and H4 visas.

P.S. : This is not an expert legal advice.