I’m not Rinnie or whoever you’re addressing, but I’ll answer anyway.
The Catholic Church does NOT rely only on the NT. I don’t recall anyone on this board who is a member of the Church stating that. If you’ve ever attended Mass, read the CCC, listened to the Pope, etc, you would know that we incorporate OT & NT in our liturgy. We use principles from the OT & NT in shaping our doctrines, dogmas, and even apologetics. However, we also have Tradition which includes the Magesterium of the Church. However, all of the statements made in the OT are not enforced any longer. Some of the prohibitions - eating of swine for one - have been completely done away with b/c they were two-fold. One purpose was for God to request obedience. The other purpose IMO is that they were sanitary. In the days of the OT swine carried diseases that humans could catch. While they still do (called a zoonosis & more common between humans & pigs than humans & cows or horses, etc b/c of similarities of antigen-antibody complexes on internal organs), we have advanced technologically, medically, and sanitarily to remove the dangers (for the most part). The same can be said for the treatment of lepers, the ‘possessed’, the alien, etc. Jesus himself followed most of the rules of Judiasm, but some he did not. He regularly met, dined, and stayed w/ aliens, prostitutes, tax collectors, gentiles, etc. He did not strictly follow the Sabbath (he cured the blind man, etc). The biggest was what he asked his disciples to do - eat his flesh. That’s obviously a big no-no in the Jewish culture. However, it has been interpreted since the early Church that this command is the primary difference between true believers & non-believers.