CrPC aur BNSS mein kya fark hai?

Main toh kafi confused hu, sab kuch read kar raha hoon lekin abhi tak samajh nahi paa raha. Pehle kisi bhi case mein jo bhi police karta hai, woh CRPC ke under hota hai na? F.I.R. lodge karne se lekar investigation till charge-sheet ke bich mein kuch bhi karna hai to kya CrPC aayta hai. Ab yaha BNSS aa gaya, to kya yeh bhi CrPC ke under hai ya alag hi kuch hai? Kya ye state level ki law hai? Toh main yeh toh samjh raha hoon ki BNSS se hamesha state level ke cases mein reference hota hai, lekin CrPC se to central level ke cases bhi ho sakte hai.