h1b application questions

I have an H1B currently. Now I want to apply for
a new H1B visa at a different company. However, I am
not sure whether to go there after I get my new visa
approved.

My questions are:

1. If my application is not approved, can I still work at my current place?

2. Can I still work at my current place
with my current visa if I my new application is
approved and I decide not to go to the new company?

Thanks in advance!