Java Edition:Unstable TNT
From when TNT was first added in 0.26 SURVIVAL TEST - Beta 1.6.6 TNT would ignite when broken. Later TNT was changed to be ignited from fire or a redstone signal in Beta 1.7. Older TNT will change to the new ignition when updated. However, the old ignition functionality was left in the game; if you have TNT with a data value of 1 (from Beta 1.7 - 14w10c (1.8 Snapshot)), or with explode:true (from 14w11a - 17w46a (1.13 Snapshot)), or unstable:true (from 18w30a (1.13.1 Snapshot) to 25w42a (present)), it will still ignite when punched. This blockstate is missing from 17w47a - 1.13, and updating to these versions will cause it to be deleted.
Obtaining
Transmutation
Block transmutation allows TNT's data value to be changed. In versions from Beta 1.7 - 14w10c (1.8 Snapshot), if the TNT is transmutated to a data value of 1, it would become unstable.
- Bluecrab2's Arrow Transmutation Unstable TNT Tutorial
Word Tearing and Any Falling Block via Asynchronous Threads
From 15w34c (1.9 snapshot) to 17w46a (1.13 snapshot), asynchronous block updates allow for block palette corruption, and this corruption, when combined with the registry palette type, can allow for the creation of any block that can exist, such as unstable TNT. Asynchronous block updates also allow for usage of the "generic method" to create a falling block entity of any existing block in your world.
These falling blocks may also be used to obtain their respective item, if it exists in item form, such as end portal frames. Blocks such as end gateways cannot be obtained as items with this method, as they have no corresponding item. Falling blocks also allow for the placement of both blocks that cannot normally be placed, either due to operator restrictions (e.g. command blocks) or not having an item form (e.g. end gateways).
20w14∞
In 20w14∞, it is possible to find Unstable TNT in the "gallery" dimension. To still be able to access it in later versions, the player needs to bring an Enderman to the "gallery" dimension, let it pick up Unstable TNT and transfer it back to the Overworld.
22w13oneBlockAtATime
In 22w13oneBlockAtATime, Endermen have a 1/1804 chance of spawning with unstable TNT in the End. They can place this block in any dimension and in any later version.
Updating
Unstable TNT must not be loaded from 17w47a (1.13 Snapshot) to 18w30a (1.13.1 snapshot) because this will cause it to revert to regular TNT.[1][2] Although the unstable tag was added in 18w30a, it was not until 18w30b that unstable TNT would gain the block state when updated.
See also
References