Minecraft growing wheat (water)?

Haven't played in a long time

Does wheat need water to grow?
How many blocks of earth are irrigated by a water source
If I prepare a field with a height, the block will darken after a short time, what does that mean?

Yes needs water
4 blocks
Dark = watered

Supplementing. It doesn't need water to grow, but water is much faster. There must also be enough light.

Well, wheat doesn't necessarily need water. It works without it, but it takes longer.

You don't necessarily need water, it's only there to accelerate. Even when it rains, the arable land is irrigated.

4 blocks are irrigated.

The "getting dark" means that it has absorbed water.