Java Edition version history

Pre Multiplayer
0.0.9a - First known version. [Verify]

0.0.11a - Stability increase.

0.0.12a - Water, Lava, New level generator, Render distance option.

0.0.12a_02 - Runs smoother than ever

0.0.12a_03 - Fixed bug with some players having trouble selecting tiles

0.0.13a - Level saving

0.0.13a_02 (Unconfirmed)

0.0.13a_03 - ???

0.0.14a - Many new blocks, added trees

0.0.14a_2/3 (Unconfirmed)

0.0.14a_4 - You can set spawn point

0.0.14a_5/6/7 (Unknown additions)

0.0.14a_8 - Sound test

0.0.15a - Multiplayer TEST

Multiplayer
0.0.15a - Multiplayer

0.0.16a - Server improvement

0.0.16a_2 (Unknown additions)

0.0.17a - Server improvement

0.0.18a - Custom skins

0.0.18a_2 - Improvement to text

0.0.19a - Sponge, Glass, Animated textures, Better avatars, New UI, Limited framerate.

0.0.19a_??? - Sponges no longer disapear

0.0.19a_6 (Unknown Additions)

0.0.20a - 16 cloth blocks, 2 flower blocks, 2 mushroom blocks, gold block, block selection, adminium

0.0.21a - Attempted rewrite for block picking code

0.0.21a_1 - Fixed block picking code

0.0.23 - Button graphics, options page and custom keymappings