Copyright and ownership for rejected papers that are edited based on peer review
It seems clear to me that the answer is post what you call your second draft. The first "round" is a closed chapter because of the reject decision. You should consider your new round as the round of relevance for the final publication; it is a new paper, the old is "dead". The first round draft will be so different from the final that it cannot represent the final version. If you receive a major/minor revision, it means that the submission has intrinsic values that are clear to the reviewers and editor and in such cases the early drafts carry with them enough to mirror the final product. So from this perspective the reject decision is a clear line of separation.