I saw a guide on here that states if your Castlevania 64 copy has a number engraved on the back (and not a letter engraving) then it's the 1.0 version of the game. My copy was an "08" engraved on the back and I just wanted to confirm that it's a 1.0 copy.

ah i have the same - that's the right idea yes - here's the back of my copy so you can confirm: https://imgur.com/a/zJbRxip

Yep, as long as there isn't an "A" or a "B" after it, then you have a 1.0 version!