Minecraft/Version differences

PC Gamer Demo
Based off Beta 1.3, the PC Gamer Demo was bundled with issue 214 of PC Gamer. There are a number of differences, including:

Cow
A PC Gamer logo was added to the cow texture.

Annnnnnd, this is how they actually appear in-game.

Title Screen
PC Gamer's logo was added above the Minecraft logo, pushing it down. All of the splash text was replaced with "PC Gamer Demo!". As the game will only allow you to play the PC Gamer Demo World, the single player and multi player options were replaced with options to play and reset the demo world and a quit game button was added. The version number was also removed.

In-game
Although not technically the Minecraft demo, it calls itself that. Beta 1.3 just says "Beta 1.3". However, like the offical Minecraft demo, a timer was added, lasting about five Minecraft days.

Options
The PC Gamer Demo sets the default controls to the arrow keys. Beta 1.3 and all other versions of Minecraft have them set to "WASD".

Cyan Flower
The rose flower is replaced by a cyan flower in Pocket Edition. There are currently no plans to release the flower into other versions of Minecraft.

Nether Reactor
The Nether Reactor block and Glowing Obsidian are special to the pocket edition. Nether Reactor blocks can be used in nether reactors to spawn nether spires, that are sort of like mini chunks of the Nether in the normal dimension. This replaces the Nether Portal and the Nether itself.

Glowing Obsidian
Glowing Obsidian is obsidian basically generated when the nether core reactor is activated. It glows faintly like Glowstone but has the same properties as regular obsidian (high blast resistance, requires diamond pickaxe to mine, etc.)

Stone Cutter
To craft stone bricks and such, you can use a Stone Cutter, also exclusive to Pocket Edition. This block shows characteristics like that of a crafting table, but used for stone recipes.

Camera
Only obtainable via inventory hacking, the Camera allows players to take snapshots from wherever the item is placed. It is somewhat buggy, though, and photos taken with it tend to be obscured by the camera's own smoke particles. The texture for its tripod was replaced with the red music disc in version 0.2. Its block ID is 456.

Crying Obsidian
Crying Obsidian was originally going to be used in the PC version of Minecraft for setting your spawnpoint, but they were scrapped with the introduction of beds. Its texture was present in Beta 1.3 and 1.4, but was removed in Beta 1.5. However, the texture can still be found in Pocket Edition's terrain.png.

Update Game Block
The Update Game Block is a placeholder block added in Pocket Edition Alpha 0.1.3, which uses a modified dirt texture with "update!" written on it. There is also a similar placeholder block that appears to say "ate!upd" (pictured right). Their block IDs are 248 and 249, respectively.

Pi Edition
Pi Edition 0.1.1 was released for the Raspberry Pi on February 11, 2013, but 0.1, an earlier version, was accidentally released on December 20, 2012, two months before 0.1.1's release. Pi Edition seems to be based off of Pocket Edition 0.5.0 although missing survival mode and mobs. Crafting tables and furnaces currently do nothing. The game can be easily modded with the official Ruby API.