I suggest not bothering with Godhome Pantheons, the Trial of the Fool, or the Delicate Flower quest for a Mask Shard (or three other Mask Shards since four are required for 1% progress) as they are on the more difficult/complex end of the scale.
Since you only need 100% completion, there is leeway in terms of what you need to complete.
If you need help figuring out what you need to do to reach 100% completion, refer to the completion percentage breakdown on the Game Basics page. You'll have to play through most of the game again and if you need direction, use my Classic mode guide. I will not be providing another detailed game walkthrough. I suggest doing this as your second playthrough so you can work through the game again without any time constraints to get better familiarity with the areas, enemies, and bosses for your upcoming speedrun. This would be a lot more difficult if you couldn't open the pause menu and 'Quit to Menu' before dying.
If you die, your playthrough ends and you must start over. Start a new game in Steel Soul mode, which is exactly like Classic mode except death is permanent.
