Pokémon Platinum, but I'm trapped on Iron Island

In this challenge I made my way to Iron Island on a completely Vanilla copy of Pokemon Platinum, then deleted all my Pokemon, items, money, and just gave myself the egg from Riley. I also made one more small edit, using custom rom making software, I changed the exit door or Iron Island to spit me out at Cynthia's room of the elite four. Is it possible to use only the items found on Iron Island, and the encounters available in the caves to defeat Cynthia? You'll have to find out. A few rules I instituted for this challenge, I can't level past Cynthia's ace Garchomp, and I can't use more than one species of Pokemon. I flirted with a few additional rules like making it a Nuzlocke, and I also thought about making it so I could get the endgame Registeel encounter, but I felt that stretched the rules a bit too far. Let me know what other softlockes you'd like to see me try and complete, thanks for watching :) #pokemon #pokemonchallenge #pokemonchannel #gaming #lucario #IronIsland