Construct a Nether Portal.

Destroy a Ghast with a fireball.

Kill a skeleton with an arrow from more than 50 meters.

Construct one type of each tool (one pickaxe, one spade, one axe and one hoe).

Use a saddle to ride a pig, then have the pig get hurt from fall damage while riding it.

Travel by minecart to a point at least 500m in a single direction from where you started.

Construct a better pickaxe.

Turn wheat into bread.

Smelt an iron ingot.

Use planks and sticks to make a pickaxe.

Punch a tree until the block of wood pops out.

Breed two cows with wheat.