Infinite Lives
POKE 652F,00
Removes the instruction which would otherwise decrease LivesDisplayCharacter.
652C LD HL,5FB3
652F DEC (HL)
255 Lives
POKE 5FB3,2F
POKE 654B,2F
This changes the code which sets the starting lives from ASCII 33 ("3 lives") to be ASCII 2F (which is "0 lives" minus 01).
So it cycles through an entire byte before reaching 00 again.