Escape PC to the last protected bytes with PC=v0+PC instruction, as PC is the pointer to where the program execute, go step by step iterating trough "instructions", read 2 bytes by checking last instruction.
After invalid instruction, use call subroutine instruction 2NNN to jump even further, after the CTF was over we checked that we could still use PC=v0+PC instruction.
Keep reading instructions and taking notes, decode instruction bytes to ascii.
Careful with the jump instructions as you could skip some instruction.

Original writeup (https://github.com/ShingekiNoChikungunya/write-ups/tree/master/HackTM-CTF-2020/CHIP_8_%232).