Mojang (now Microsoft) does not make old versions easy to find via the default launcher, but they are legally accessible. Here is the definitive way to play 1.2.5 today.
The 1.2.x cycle was nicknamed the "Jungle Update." It introduced:
: Added a method to quickly acquire blocks selected in the world while in Creative mode by using the "pick block" key (middle-click by default). minecraft 1.2.5 java version
Minecraft Java Edition 1.2.5 a significant, "golden age" minor update released on April 4, 2012
If you load it up expecting Minecraft Dungeons or Hypixel Skyblock , you will hate it. If you load it up with a friend, a stack of torches, and the goal of reaching The End, you will have a pure, unadulterated survival experience that the modern version has largely forgotten. Mojang (now Microsoft) does not make old versions
Warning: There is no "Drop in mods folder" in 1.2.5. You must edit minecraft.jar .
It is famously used for classic modpacks, including early iterations of IndustrialCraft 2 BuildCraft RedPower 2 Twilight Forest Authentic Feel: Minecraft Java Edition 1
: Introduced the ability to shift-click items from the player's inventory directly into their respective furnace slots.
1.2.5 is legendary in the modding community. It was arguably the last major version before the Minecraft Forge
To understand the importance of Minecraft 1.2.5, you have to look at what came before. The transition from Beta 1.8 to the full "1.0" release was rocky. The official 1.0 release (MineCon 2011) added the End dimension but was riddled with bugs. Version 1.1 fixed some issues, but was the polish patch that made everything work.