Before the Fall, Adam and Eve were vegetarians, Genesis 1:
There is no sense in thinking that God was flip flopping back and forth about whether or not it is an abomination against His eternal nature to eat unclean animals. Rather, there were no predators or scavengers before the Fall, which are all unclean animals, so nature of animal change with the Fall and it has been a sin to eat them ever since. If Adam and Eve could kill animals for clothing after Fall, then I see no reason to think that they were still restricted from killing animals for food, especially because Able kept a flock of animals.
After the flood, Noah was allowed to eat meat, Genesis 9:
But there was a catch:
Don't eat blood.
In Genesis 7:2, Noah was given instructions for what to do in regard to clean and unclean animals without being told to how to tell the difference, and in 8:20, he knew to offer a clean animal, so he must have already been given instructions in that regard. In Psalms 119:29 and Exodus, the wanted God to be gracious to them by teaching them to walk in His way in obedience to His law, and in Genesis 6:8-9, Noah found grace in the eyes of God, he was a righteous man, and he walked with God, so God was gracious to him by teaching him to walk in His way in obedience to His law and he was righteous because he obeyed through faith. In Genesis 9:3, the word used refers to prey animals, so Noah was being given permission to eat prey animals, which refers to clean animals. In Genesis 6:21, Noah was given a temporary restriction to eat the same food as the other animals while on the ark, which was for obvious reasons, so Genesis 9:3 is the lifting of that temporary restriction.
For the Israelites, Leviticus 17:
Furthermore, there was a refinement between clean and unclean Food, Leviticus 11:
Sin was in the world before the law was given (Romans 5:13), so there were no actions that became sinful when the law was given, but rather the law revealed what has always been and will always be sinful.
Targeting the Gentiles, the Lord told Peter in Acts 10:
There were all kinds of animals let down in Peter's vision, so he could have obeying God's commands in Leviticus 11 and Deuteronomy 14 and God's command in his vision by simply killing and eating one of the clean animals, so understanding why he refuse to do what the Torah permitted him to do is the key to correctly understanding his vision. It should be noted that Peter did not just object by saying that he had never eaten anything that was unclean, but also added that he had never eaten anything that was common, these words are not used interchangeably by the Bible, and God only rebuked Peter for his use of the word "common", but did not rebuke him for his use of the word "unclean". In other words, Peter had correctly identified the unclean animals as unclean and had correct declined to eat them in obedience to the Torah, but he had incorrectly identified the clean animals as common and had incorrectly declined to eat them in disobedience to God's command to kill at eat. Peter interpreted his vision three times as being in regard to incorrectly identifying Gentiles without saying a word about now being able to eat unclean animals, so his vision had nothing to do with a change in their status. You should be more careful not to mistake what was only said against following the traditions of men as being against obeying the commands of God.
James arrived at a compromise between the influences of Jews and Gentiles, Acts 15: The Jerusalem Council declared in Acts 15:
Either Acts 15:19-21 contains an exhaustive list of everything that would ever be required of a mature Gentile believer or it does not, so the moment that you treat it as an non-exhaustive list by saying that there are obviously other commands that Gentiles should obey is the moment that you can no longer treat it as being an exhaustive list to limit which laws Gentiles should follow. For example, Gentiles should follow the Ten Commandments, the greatest two commandments, and those things commanded against in 1 Corinthians 6:9-11, Galatians 5:19-21, and Titus 3:1-3. However, it was not given as an exhaustive list for mature believers, but as stated in Acts 15:19-21, it was a list intended to not make things too difficult for new believers, which they excused by saying that Gentiles would continue to learn about how to obey Moses by hearing him taught every Sabbath in the synagogues.
In the final analysis, for us today, Mark 7:
There are a whole host of problem that you should have with the way that you are interpreting Mark 7:19 as Jesus setting aside the commands of God starting with the fact that he had just finished criticized the Pharisees as being hypocrites for doing that. In Deuteronomy 4:2, it is a sin to add to or subtract from the law, so Jesus did not do that. In Deuteronomy 13:4-5, the way that God instructed His people to determine that someone is a false prophet who was not speaking for Him was if they taught against obeying His law, so if Jesus had done that, then according to God we should consider him to be a false prophet. They would not have needed to find false witness at his trial, but this incident was never even brought up, and no one seemed to have even noticed that he made such a radical statement in rebellion against the Father. It is far more reasonable to interpret this passage and Jesus simply continuing to speak in regard to the topic of conversation.
Paul was emphatic, Romans 14:
Romans 14 is speaking in regard to disputable matters of opinion in which God has given no command, so nothing in the chapter should be interpreted as teaching us to rebel against God.
Foods law was strange teaching, Hebrews 13:
What God has taught is not strange teaching.
The Colossians were keeping God's holy days in obedience to His commands in accordance with the example that Jesus set for us to follow, they were being judged by pagans for doing that, and Paul was encouraging them not to let the pagans judge them and prevent them from obeying God.
It is reiterated in 1 Timothy 4:
In 1 Timothy 4:1, Paul described what he was speaking against as being the doctrine of demons, which should be a major clue that he was not speaking against obeying the holy, righteous, and good commandments of God. We know that Paul interacted with pagans in Colossians 2:20-23 who were promoting human precepts and teachings, self-made religion, asceticism, and severity to the body. In other words, they were teaching against eating the clean animals that God said were good to eat as food in Leviticus 11 and Deuteronomy 14.
In fact, demons will make dietary requirements.
In Psalms 119:142, God's law is truth, so those who know and believe the truth know that we do not need to refrain from eating clean animals that God created to be received with thanksgiving and that unclean animals have not been sanctified by the word of God and prayer, so we should not receive with thanksgiving that which God said is an abomination.
Jesus gave us the freedom to eat. Follow your conscience.
The clearest sign of someone having a seared conscience is if they see nothing wrong with continuing to do what God has revealed to be sin, which should indicate to them that they have a serious problem, not that there is nothing wrong with what they are doing.
