It means USCIS denied the visa, and the Board did not agree with them and they took away the denial and sent the visa back to USCIS. You should be scheduled for an appointment to complete adjustment, if that's what you filed.
1. Neither, you can do this yourself.
2. You can remain on your H1b until your change of status is granted.
4. Your employer must revoke your H1b if you are no longer an H1b and this should have no effect on any PERM application the employer is filing, nor on an I-140, unless you are asking about extension beyond the 6 year limit.