I would want to know if there is a sort of "
undo" command in Minecraft (no mods) that undo one action at the time. For example, the player pressed a button that started a huge redstone system or he detonated one TNT that detonated other TNTs.
No, there is no built-in undo system.
However, if you are prepared for it, you can use the
/clone command. You'll want to clone the part of the map (periodically) you are working on to another, far away area. Then, if you want to "undo" this, simply reverse this cycle, and clone the "backup" area into the "work" area.
Tip: Make sure not to clone from the building area constantly, because that destroys the whole purpose of this. Make sure you clone it every so often; maybe every day-night cycle?