Can i use sealed precooked ham 4 weeks after its sell by date?

No, you should not use sealed precooked ham 4 weeks after its sell by date. The sell by date is a guideline for when the product is at its peak quality, but it does not mean that the product is unsafe to eat after that date. However, the quality of the ham may have declined and it may not be safe to eat. It is best to discard the ham if it is more than 4 weeks past its sell by date.