What to strategically do when you take JLPT N3 in 3 days and are late?

[DIO-Berry]

I wrote a guide for this sort of thing

Berry's JLPT and General Test Prep Guide and Checklist

Night before the test Pack your bag, so you just just grab it and be ready to go in an instant. Make sure your transportation is planned and prepaid if possible. How long does it take to arrive? What happens if you run into traffic or your bus/train is delayed? Did you check that your car has gas? Etc, etc. Have a time cushion or barrier train/bus to ensure that you arrive on time. Get a good night’s sleep, or at least give yourself enough time to get a good night’s rest. You want to be in…

tldr: Get a good night’s sleep several nights in a row and eat healthy

If you try to study kanji and vocab now, odds are that your long term retention won’t be active for those kanji and words yet. I would recommend reviewing/testing that doesn’t stress you out at this point. Kotoba’s discord bot seems like it could be a good one. You can try to improve your speed and expose yourself to kanji and words you don’t know well with the N3 deck. There are probably other ways too, but that’s the only one I can think of that would be closer to comprehensive and also not involve dumping like 10h of study into each day.