Does this work in Java Edition?

It's a 1/8192 chance of encountering a shiny Pokemon. It's all up to Lady Luck whether you find one or not.

This is not possible anymore. The offer to have gotten a free code for buying Java Edition is now expired.

In the create new world menu, just scroll down until you find the "world type" area. Then click on where it says "infinite" and select "flat" from the drop down...

SKSE hasn't been reworked for Skyrim: Special Edition. I don't believe the original creators plan on doing it, either.

Sadly, no. You can only do this in Java edition Minecraft, upon installing the Aether Mod.

Unfortunately, no. As of the time this answer is written (Dec 1, 2020), the Bedrock Edition (formerly known as Pocket Edition) of Minecraft still doesn't allow for custom Superflat worlds....