Hardcore mode has been added ever since Java edition 1.0.0. In hardcore mode, players can no longer respawn upon death, and the difficulty is locked to hard. This mode is very popular in the Java edition.
Select version for changelog:
Updated compatibility for 1.16, fixing several issues regarding bypassing death and reviving.
then, separately type:
/tag fly12jacka12jk remove dead
1. Change your rating to 5 stars
2. Create a new world and set it with your desired settings. MAKE SURE ALL EXPERIMENTAL FEATURES ARE OFF AS WELL AS CHEATS.
3. Set it onto hard difficulty.
4. When you die, turn on cheats, go on creative and drink invis.
5. Realise you are stupid and should just use the behaviour pack.
Note: this only works on singleplayer and instruction 5 only applies to Wacky Wars.
However, it is a feature only available when education is enabled.