It doesn’t matter how you cook it, cooking it thoroughly will kill the bacteria. However, some bacteria leave toxins behind and cooking won’t get rid of those. Basically don’t eat rotten meat, the best way to tell if it’s rotten is looking for discolouration and it smelling really bad, although this can also be a good thing in some aged meats like game or beef. BTW, beef turning brown when the packet is opened is normal. Supermarkets fill the packets with inert gas to artificially keep the meat looking red.