Before you hit publish, do you need your ISBN, LCCN, and Copyright Registration all in line?

No.
The only one you NEED in order to publish is the ISBN. I always recommend having your own so you can take it anywhere with you.

The LCCN you can get later, but I always say to have it before hand so you don’t have to go back and redo the interior later. It takes up to 6 weeks to get the truly free LCCN from the Library of Congress

Copyright registration can take months so you can publish without it or while the application is pending.

Best of luck!