First of all, we're going to make the game a LOT easier by using cheat codes. You can skip the cheat codes and still run through the game in the order I list in the guide, but it'll be a bit harder. Whether or not you use the God code is completely up to you.
There is a code for getting all the items. DO NOT USE THIS CODE. There is an achievement tied to obtaining each item, and the achievements don't unlock with the code. Therefore while you'd otherwise be able to travel straight to the boss with all the items, you'd miss a lot of the achievements.
Note: before you use the code, make sure to kill yourself 3 times for that achievement. It just makes things easier.
To unlock god mode, pause the game, then press . Then go to Cheats and turn on god mode. Easy peasy.
On to the game...
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