You’ll get a lot more responses if you move your post to the UNOFFICIAL categories. General users can post in there, and not in OFFICIAL channels.
As for your question, I think it would be fine if you specify that you are going back to the past. You’ll want responses from Event Partners, though. They run the events, and will make the call if a team were to show up in your position.
You would still be eligible, but this may be taken into account when deliberating.
Last year, I forgot to update my book for a couple of days and just went back and did it later. I don’t feel bad about it because it wasn’t a whole slew of information. But, I have more free time during the day now, so I shouldn’t have to.
The best option at this point is to record, as fully as possible, the progress you made in the order you made it. Document it with any photos you took at the time, or take some still shots out of videos. Timestamps on those can help you get things in the correct timeline. Draw/sketch parts and subsystems that you worked on along the way. Presumably, you had discussions among team members about what approach to choose; put that in the notebook. If it was just one person making the decisions, get that person to describe their thought process, and document. Often, those kinds of decisions can be put into a text/numeric chart even if you didn’t do a formal decision matrix.
Where you made choices that didn’t work, be sure to include that. As Mythbusters taught us, “Failure is Always an option.” Be sure to capture those in the notebook to the degree possible. The idea (when doing this professionally for work) is to show why a failed approach didn’t work. That way the team picking up your work in the future won’t waste time on approaches that aren’t fruitful. Remember, these notebooks are about demonstrating you’ve learned how to document a project, warts and all.
The important part is to capture to a high degree of completeness the process you went through to build and program your robot. The goal should be to walk someone through your process, showing them you did the work, and you didn’t just pick up a robot someone else built.
You should date the pages with two dates: The approximate date, to the best of your determination of when the work described actually occurred, and the CURRENT DATE, at the time you are recording the information. Sign the pages for the current date.
Creating the documentation contemporaneously when the work is performed is best. However, if you do what I’ve described here, you’ll be fine. It will take a while. But the notebook will be a very good representation of your work. Be honest about the dates, and if a judge asks about it, explain what you did. Make it clear you’re being honest, and being thorough. You won’t suffer for it.