How to make my own Open World game, and which software is required

You have to use any Readily available Game Engine if you’re an indie developer.

Otherwise you can use the engine that your company provides you.

SOME OF THE GAME ENGINES ARE AS FOLLOWS :

Unity engine:

One of the Best for Android game development.

Unreal Engine

Overall Best. Award the title of best game engine in Guinness Book of World Records.

Cry engine

And many more

Here is the list link

List of game engines - Wikipedia

Personally I am also an indie developer learning Unreal engine because Its The Best according to me.

Advantages

  1. Lots of tutorials on youtube
  2. Helpful forums
  3. Blueprint system,can use blue prints and make a game without writing single line of code
  4. Along with blueprint you can also use C++ cosing if you are comfortable with it.
  5. Variety of platform support
  6. You can make a game and then package it for both Pc, mobiles and consoles
  7. The provides templates and starter contents to help beginers
  8. Huge market place of Assets and blueprints, both free and paid.
  9. Its FREE unlike Unity.
  10. The will only charge Only if you Cross $3000 of quarterly revenue, otherwise not a single penny.

Hope you got my points clear. I am a Pharma Student but I am learning ing to develop Games As My hobby and side business…

So for a no investment startup at its the best

Although you'll need a powerful PC to develop games.