can i hold both h4 and h1b

My spouse got her h4 visa stamped… Now in her office they are initiating h1b for her… So my question is

  1. Can she hold both h4 and h1b visas at the same time
  2. Can she travel in which ever visa s she wants to ?
  3. Will her h4 visa be cancelled when she appears for h1b-visa ?
  4. Or she can just file her h1b pettition and travel on h4 ?

Kindly clarify my doubts. Thanks in advance