I just heard that the F1 student is better to file 485 after 90 days of entering US. My son and I had a short visit to Cananda about three months ago. He entered US with his F1 approval notice (changed from H4 to F1 ten months ago). We filed his 485 a few days ago. Now I realized that our filing is not over three months after his entering US (maybe around two and half months). Do we have a trouble for this? Can you explain more on the 90 day rule? Thank you for your help.