Creating a multiplayer RTS (Real Time Strategy)?

Question

C++ / C#

Example https://store.steampowered.com/app/227180/Kingdom_Wars/ created by indie developers.
There is an idea, the basis is taken from the game above. Apparently, you need to cut your engine, I know a little different languages.
I know +- as a native language, without libraries and packages java, c++, c#. Basic javascript, php. For a couple of years of work, there is already a certain representation of client-server applications.
Previously, I worked a little with Unity and Unreal, but everything is visualized there. Everything ended on demo projects in which I dug. In my case, it will be necessary to cut in Visual Studio, as I understand it, perhaps not only for drawing graphics.
Now I'm looking for ways to decompile and dig into the game code and see what's under the hood. Mount & Blade and the example game. So far no idea how to put it all together.
1 - Will my custom engine look essentially the same as Unreal or Unity?
That is a UI view for navigating the project, changing its files?
2 - Where to dig what to learn, books, guides? There is no mentor, you need an adequate guide.
3 - What software?
4 - And where do you start after an idea in the development of PC games?) e
5 - is there a demo of engines on the same github for similar games or for a beginner?
6 - how does the server part work? In terms of updating the player's position for other players?
7 - Setting up a server for the game? Since this is purely an online game.

Answer 1

It seems to me that if you have such questions, then you are not ready for either the development of an MMO or an RTS.
In such cases, it is usually advised to make a simple Pong, and then other questions will appear.

Answer 2

Just a tip: look at casual. MMO RPG is not an indie genre, and the release of such games is rather an exception.