can I freeze chicken defrost it and eat cold for lunch?
That's perfectly fine, assuming the meats were cooked properly originally. If you look up people doing bento lunches, they use freezer staples a lot; often, if the item is small enough, it can be packed in a lunch still frozen and be defrosted by lunchtime. However, if you're talking about a whole steak or chicken breast, you'll want to stick it in the fridge overnight to let it defrost first.