Exit a level on fire with 1 health remaining to have infinite health. You cannot get any health bottles. The easiest place to do this is the sleeping village because of the boiler guards near the end of the level.
To unlock Cheat mode, pause the game, then hold R and press DOWN, UP, SQUARE, TRIANGLE, TRIANGLE, CIRCLE, DOWN, UP, SQUARE, TRIANGLE. A "Cheats" option will now appear towards the bottom of the menu, with "Invulnerability" and "Have All Weapons" options.
To get the Woden's Brand sword, get a Gold medal in all eight mini-game challenges. Then, go to a shop Gargoyle and exchange the eight tokens for the Woden's Brand, which is the most powerful sword in the game.
After saving the farmers in the Haunted Ruins level, follow them to get a large stash of gold. Walk back to the bridge, save the game, and reload it to have the gold reappear. Repeat as desired. It takes only a few minutes to get over 2,500 gold.