You’ve asked two questions, and we’ll look at them one at a time.
Sex before marriage
In the New Testament, there’s the phrase ‘sexual immorality’ which translates a word meaning ANY sexual activity outside of marriage. This means that sex with anyone that you’re not married to is sexual immorality, even if you’re engaged to them. It was assumed in both the Old Testament and the New Testament that both men and women would remain virgins until marriage.
In the Old Testament, for example, Genesis 38:24 shows the reaction to the news that a woman has had sex outside of marriage. And Exodus 22:16 shows that a man who has sex with a woman is expected to marry her. This is because the proper place for a sexual relationship is in marriage.
The clearest chapter in the New Testament is 1 Corinthians 7. The only ways to avoid sexual immorality are to abstain from sex as a single person, or to get married and then be faithful to your spouse. Notice in verse 39 that when a Christian has a choice about who to marry (that is, their marriage isn’t arranged for them), then they should marry a fellow Christian.
God designed sex as his gift for marriage. You give your body to your spouse and they give you theirs. It’s meant to build a bond that lasts a lifetime, with the potential to create children as well.
In the Old Testament, God told his chosen people, the nation of Israel, not to eat pork (e.g. Leviticus 11:7 and Deuteronomy 14:8). God outlines why he made these rules. For example, later in Leviticus 11 (verses 45-47), God says that it’s because he is holy. That means he is set apart, separate from the world. And he is perfect. And he demands that his people be like him, distinct from the world. The Old Testament food laws were a sign or reminder to Israel that they were to be a holy nation, different from the other nations.
In the New Testament, the coming of Jesus changed these food laws. He said that food doesn’t make us unacceptable to God (Mark 7, especially verse 19). The apostle Peter saw a vision that declared all food allowable (Acts 10-11, especially 10:12-15). This meant that because of Jesus’ death and resurrection, people from all nations were welcome to be part of God’s people, not just Jews. The food laws no longer had any purpose.
The apostle Paul talks about food in Romans 14 (especially verses 14, 20-21). We are free to eat anything we like, but we shouldn’t eat something if we think it’s wrong. We should also consider not eating something if it offends someone we’re with. This is Christian love, putting the other person’s needs above our own. And we shouldn’t judge those who eat something that we don’t eat, because God accepts them.