Eating expired meat as long as it's remained frozen is safe.
But it's never okay to eat spoiled meat even if the meat has remained frozen and you cook it all the way through.
Spoiled meat contains bacteria that can make you deathly sick if you eat it and it will taste awful.
If you eat spoiled meat you'll get food poisoning and be vomiting have diarrhea and severe stomach cramps.
If you eat spoiled meat it will make you sick and you should go to the doctor or emergency room because you might get some severe food poisoning.
Even when you cook the spoiled meat it doesn't mean it's okay to eat.
Spoiled meat should always be thrown out and never eaten to prevent health issues.