Minecraft wiki entry for Hardcore_mode, associated text: Some players choose to save a back-up of their hardcore world in case they die (especially before entering The Nether, or The End). Many people consider this cheating, as it can "ruin" the feel and purpose of Hardcore mode.
Game rules can be used to increase difficulty. Example: In ultra hardcore mode, natural regeneration is turned off. The only way you can regenerate health is by consuming golden apples, enchanted golden apples, fully powered beacon or by using potions, for example, Instant Health or Regeneration.
Command: /gamerule naturalRegeneration false
You can also turn on reduction of debug info, making it far easier to get lost in a world, and practically mandating the usage of maps and compasses.