How do I get to the hidden levels?

By looking at the source, I’ve found a couple of ‘hidden’ levels, but not how to get to them. They are as follows:

Cow level

  • Do the starting abilities actually do anything?
  • What effects do the sword enchantments have?
  • How do I lower my hitpoints?
  • Will using Javascript sorcery have a negative effect on the game?
  • What are the correct answers to The Frog's questions, and what is the reward when I get them all correct?
  • How do you defeat yourself or: How do I defeat myself?
  • How do I get to them?

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