Please Help - Dimensions and Biomes

I need help with dimensions and biomes.

Biomes

     1 - I want to make biomes have different heights.

         (example: my mountain biome will have mountains, my plains biome will be a bit flat.)

     2 - I want a 100% FLAT biome, like the superflat option.

Dimensions

    1 - I want a dimension with a custom deepslate and custom bedrock.

    2 - I want to make items be the portal igniter, like nether portals use flint and steel.

PoisonousPotato