Currently on H4, need to resume on previously approved H1B (currently valid)

[ridi]

I had an approved H1B visa (stamped) with an employer but did not get a project, So I applied for a dependant visa H4 since my husband is in USA.

I got the H4 approved. The H1B stamp got cancelled during my H4 visa stamping process.
I applied for a sabbatical (long leave) with my company/employer and they did not cancel my petition.

I entered US on H4 Status. Meaning I am still employed with the petitioner of the approved H1B, but on leave.

The Company agreed that if they do get a project they will let me know and I can resume working on new project.

My question is, when the employer gets a project, how do I go start working?

1) Does the company/petitioner of the approved H1B have to re-file a new H1B?

** 2) **Can I get visa stamped again on the same previously approved petition for which I had earlier got a stamp (which was cancelled during H4 stamping)?

3) If answer to question 2 is yes; then Can i exit and re-enter on the previous existing approved H1B with newly stamped H1B visa?

Thanks for your help!!!!