You can always check out our guide to Witcher 3's level cap right here, or get a true mastery of magic with our full guide to signs and spells here.
Of course, there's a lot more to Witcher 3 than cooking up burgers. Meat can be found in your inventory in the food and drink menu, but you'll need mods if you want to cook any of it. Features On-the-fly, in-game customizations to tweak skill level to your own liking Enable / disable toggles to turn features you like on / off New skill. Keep in mind that this is only available for those on PC. A current popular example is the 'What's For Dinner' mod by Az0r3, which allows you to make numerous recipes from food ingredients, similarly to making oils and elixirs in the alchemy menu. If you are intent on setting up a Temerian barbecue, you'll need to use mods that enable you to cook. ('The Witcher 3MODS') 4) Use Script Merger if you have other mods that use guiBaseInventor圜, , or inventor圜. Feel free to eat it without fear of penalty, but be aware that it's almost never as good for healing as cooked or prepared food, usually offering a lesser regenerative effect for half the time.
Geralt can eat any meat he gets hold off as he would any other food item, and suffers no ill effects for doing so (Witchers are canonically immune to most diseases, so presumably that includes food poisoning too).
No, surprisingly enough, or at least not without some alterations to the game.