The pattern is always different. Go to the gypsy where you started the quest. She will tell you the code again. I suggest writing it down.
Chat with our AI personalities
I would say you should be level 50+. You could be lower but with better food.
A quest walkthrough for Demon Slayer can be found here: www.runescape.wikia.com/wiki/Demon Slayer
If this is part of the Demon Slayer quest, then the link below should direct you to your answer.
look on runehq
By doing Demon slayer quest