To download and play , the final bug-fix update of the Alpha era (released December 3, 2010), you can use the official launcher or community-made alternatives designed for "Golden Age" versions. Method 1: Official Minecraft Launcher
If you want to revisit the roots of the game, use the rather than downloading files from unofficial websites. How To Play Old Minecraft Alpha | Step By Step minecraft alpha 12 6 download updated
You have purchased Minecraft Java Edition before the game’s full release (or have a modern account that includes all old versions). To download and play , the final bug-fix