Terraria – How to play the iOS/Android tutorial map on PC

The mobile and PC versions of Terraria have different content and are not compatible with each other. This might change in the future, but it seems unlikely at the time.

No, it is not infinite, see the wiki:

• Players may attempt to drain the ocean by tunneling down to the Underworld, where water evaporates. The Ocean is in fact drainable this way, and this method will allow the player to go back to the Ocean floor and easily pick up all the Coral without worry of suffocating. However, no Sharks will spawn once the Ocean is drained, and previously-spawned Sharks will have vanished. Therefore, draining will not allow a player to obtain Shark Fins and the Diving Helmet.
• Another way of draining the ocean is by making an air pocket, empty a bucket of lava in it and place an object that can't be destroyed by lava in the lava. After that allow the water to flow into the lava. The object will prevent obsidian from being generated, causing all the water to disappear.