Baked potatoes keep 4 days refrigerated, unfilled. Reheat at 400°F for 15 minutes to re-crisp the skin. Don't leave cooked potatoes sitting warm for hours — wrapped baked potatoes held at room temperature are a known botulism risk.
50–60 minutes at 425°F for a large russet. Microwaving 5 minutes first then baking 20 speeds it up, though the skin is never as good.
Not if you want crisp skin — foil steams them. Wrapping is only useful for keeping them hot after baking.
A skewer slides in with no resistance and the skin feels papery. That's around 205°F internally — potatoes need to go well past 'hot' for the starch to turn fluffy.