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USDA guidance gives most properly refrigerated cooked meat and leftovers 3–4 days at 40°F / 4°C or below. That window assumes the food was refrigerated promptly; reheating later cannot make up for hours spent warm.
There is no single refrigerator limit for all raw meat. USDA gives raw steaks, chops and roasts of beef, pork, veal and lamb about 3–5 days at 40°F / 4°C or below, while ground meat and many organ meats get only 1–2 days.
Raw ground meat has a short refrigerator window: USDA recommends cooking or freezing ground beef, pork, lamb or veal within 1–2 days at 40°F / 4°C or below. Grinding spreads surface organisms through the meat and greatly increases exposed area.
Cooked rice is safest when it is cooled quickly, refrigerated within 2 hours and reheated evenly to 165°F / 74°C. The key hazard is not reheating itself: Bacillus cereus spores can survive cooking, and heat-stable toxin may form if rice spends too long warm.
USDA recommends cooking or freezing fresh raw chicken within 1–2 days when the refrigerator is 40°F / 4°C or below. Smell and color can reveal obvious spoilage, but they should not be used to stretch that storage window.
Persistent off odor, a slimy or sticky surface, mold or obvious deterioration are reasons to discard meat. Color alone is less reliable: meat can turn brown as myoglobin changes without necessarily being spoiled, and meat that looks normal can still be unsafe if time or temperature limits were exceeded.
The green pigment itself is chlorophyll and is not toxic, but greening signals light exposure that can also increase natural potato glycoalkaloids such as α-solanine and α-chaconine.
Finding two small sprouts does not automatically condemn a potato. Look at the whole thing: firm and not green can usually be trimmed; heavily sprouted, green, soft, shriveled or bitter is a throw-it-out potato.
The leftover question does not really start on day three. It starts when dinner ends: prompt cooling and a cold refrigerator are what make USDA's 3–4 day window meaningful.
The freezer is not the real question; the thawing history is. USDA generally allows refrigerator-thawed food to be refrozen raw if it stayed cold, while microwave- or cold-water-thawed food should be cooked first.