Most leftovers are good after 7 days depending on what kind of leftovers they are and whether they were frozen or just refrigerated.
If the food contains any meat and was refrigerated only for those 7 days then no the food and leftovers would be no good to eat after 7 days and should be thrown out because bacteria can grow on the food and meat.
If the food was something such as noodles or any other food without meat then the food leftovers in the refrigerator should still be safe to eat after 7 days.
Just look at the food and smell it and if it smells good and has no mold in the food then it's likely safe to eat after the 7 days.
But if it smells bad or has mold or tastes bad then throw it out.
If the leftovers were frozen then yes they can last 7 days and longer as the freezer temperatures keep bacteria from forming in the food.