Just close the door and forget about. Not worth getting all stressed and wound up by a small thing like this. One thing i learnt from experience: it takes a lifetime to be wise.
Correct. You can go late up to 7 days after or 14 days before. You can do the first report by post as long as it arrives before your due date. Since you report to the local provence immigration send by post should not take more than 3 days. Offical docs: