I have a valid B1 visa. My spouse is holding an H1 visa and I would like to go as a dependent [H4]. If I apply for an H4 now will it invalidate my B1 visa?
You will not invalidate your tourist visa by applying for H4. While you wait for your H4, you should probably not travel to the US because people tell scary unbelievable stories which accidentally may be true in some extreme marginal cases, and you don't want them to happen to you. After all, people in the US who work as border control inspectors do that for a reason, which is mostly because it makes them feel powerful.