A friend of mine says pork was prohibited in the Old Testament, but keep reading, changes happen in new Testament.
God gave Peter a vision in which He declared all formerly unclean animals clean (Acts 10:15)
You quoted from your friend: "God gave Peter a vision in which He declared all formerly unclean animals clean (Acts 10:15)"
I quote the relevant parts from the book of Acts so that the whole picture can be seen, I am replacing the parts that are not relevant with dots but obviously you can check the entire message yourself if you prefer:
11 He (i.e. Peter) saw heaven opened and something like a large sheet being let down to earth by its four corners. 12 It contained all kinds of four-footed animals, as well as reptiles and birds. 13 Then a voice told him, "Get up, Peter. Kill and eat." 14 "Surely not, Lord!" Peter replied. "I have never eaten anything impure or unclean." 15 The voice spoke to him a second time, "Do not call anything impure that God has made clean." 16 This happened three times, and immediately the sheet was taken back to heaven. 17 While Peter was wondering about the meaning of the vision, the men sent by Cornelius found out where Simon's house was and stopped at the gate. ... 19 While Peter was still thinking about the vision, the Spirit said to him, "Simon, three men are looking for you. ... 28 He said to them: "You are well aware that it is against our law for a Jew to associate with or visit a Gentile. But God has shown me that I should not call anyone impure or unclean.
Please note the underlined parts in the above quote from the books of Acts. As it is clear the dream that Peter had was (like many other dreams) a symbolic one. This is why he was wondering what it meant. It is only later that he realises what the meaning of the dream was. Peter, as evident from above, interprets the dream to mean that Jews are not superior to Gentiles (non-Jews) as no human being is impure or unclean.
As you see this has nothing to do with the law about what to eat and what not to eat. In fact, if the meaning of the dream to Peter was that all animals were clean enough to be eaten, then why in Acts 15 the apostles including Peter are deciding what should be considered impute food for Gentiles?
Further, more important than a vision by an apostle is the words of Jesus (pbuh) as quoted in Matthew 5:17-20:
17 "Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them. 18 For truly I tell you, until heaven and earth disappear, not the smallest letter, not the least stroke of a pen, will by any means disappear from the Law until everything is accomplished. 19 Therefore anyone who sets aside one of the least of these commands and teaches others accordingly will be called least in the kingdom of heaven, but whoever practices and teaches these commands will be called great in the kingdom of heaven.