DS-160 application with H1B receipt

[docsb]

Hi

My H1B petition was receipted by USCIS on Oct 1st under premium processing. I know it takes 15 calendar days for their decision. I wanted to know whether I can apply for the DS-160 electronic visa application in advance (with the H1B receipt number) so as to get a bar code number to secure a tentative appointment date. I have to go to the U.S Barbados embassy for visa stamping and I live on a nearby island so can potentially fly to barbados the very next day for the visa interview once I receive the H1B approval documents.

Secondly, does the NIV appointment website allow us to reschedule the appointment date ?

Thanks

Sumshe