Therefore by the deeds of the law no flesh will be justified in His sight, for by the law is the knowledge of sin. If you asked ten different people you may get up to ten different responses. How are you to know the truth of the matter.
Truth is a statement of fact.
God is truth. There can only be one God and one truth, everything else is false. So for each of those questions listed above there can only be one correct answer, everything else is a lie. There are two sources where you can find theses answers. God is the ultimate authority so that is where you must go for the answers.