H4 & H1 COS - need clarification - plz help

My husband is in US on H1b. I would like to work in US, still didn’t go there from India. As per my knowledge many employer start finalizing candidates for h1b processing by January.

  1. If I apply for H4 here(India) first & with out traveling to US, can I apply H1b separately later from a employer from India or US. If this is feasible do they(employer) need to apply Change of Status(COS) from H4 to H1 in April or do I need to inform in January only?

  2. If I apply for H4 here, do I need to visit US at least once? Then only they can change from H4 to H1(COS)? How to approach the employer on this?

  3. With out COS, can I apply H1b separately & H4 separately in parallel?

Please clarify?