Are you Scott Hahn?
Okay, everything you say is true, but you haven’t answered the question. If Jesus celebrated the Passover meal on Thursday, why were th sacrifcial lambs being slaughtered on Friday? Why was Friday the Preparation day?
No, I am not Scott Hahn…

That was a debate I was challenged too, on a Protestant forum, where I am the only Catholic.
Friday started at sunset Thursday according to Jewish interpretation. I realize this only brings us to the day of preparation, but it also brings us to the day the Lamb of God was “slaughtered”. How could Christ have celebrated the Passover ahead of schedule?..
With Christ knowing His hour was to come, He also knew the timeframe things would take place.
Joh 13:1 Before the festival day of the pasch, Jesus knowing that his hour was come, that he should pass out of this world to the Father: having loved his own who were in the world, he loved them unto the end.
Knowing the timeframe, Christ still had a desire to eat the Pasch with them.
Luk 22:15 And he said to them: With desire I have desired to eat this pasch with you, before I suffer.
So, things happened according to His desire, or “will”.
Even though it was a new covenant, fulfilling the prophesy of Jeremiah 31:31, it was unlike the covenant with their fathers. Even though it was unlike, it was of the same typological sense.
The prophesy of Jeremiah 31:31 is quoted, word for word, in Hebrews 8:8 - 12, but I suggest reading the larger passage of Hebrews 8:6 - 13.
**Heb 8:6 But now he hath obtained a better ministry, by how much also he is a mediator of a better testament which is established on better promises.
Heb 8:7 For if that former had been faultless, there should not indeed a place have been sought for a second.
Heb 8:8 For, finding fault with them, he saith: Behold the days shall come, saith the Lord: and I will perfect, unto the house of Israel and unto the house of Juda, a new testament:
Heb 8:9 Not according to the testament which I made to their fathers, on the day when I took them by the hand to lead them out of the land of Egypt: because they continued not in my testament: and I regarded them not, saith the Lord.
Heb 8:10 For this is the testament which I will make to the house of Israel after those days, saith the Lord: I will give my laws into their mind: and in their heart will I write them. And I will be their God: and they shall be my people.
Heb 8:11 And they shall not teach every man his neighbour and every man his brother, saying: Know the Lord. For all shall know me, from the least to the greatest of them.
Heb 8:12 Because I will be merciful to their iniquities: and their sins I will remember no more.
Heb 8:13 Now in saying a new, he hath made the former old. And that which decayeth and groweth old is near its end. **
Personally, I believe we received a “better” passover, than with the old covenant, which decayeth…