Modding Help

I need help with coding a mod. Specifically, a mod that adds a mob with a new item drop. I have C++ coding experience, and I know how to save as a class file, I just need help as to what to put in the file. I tried Youtube, but most tutorials are either lowly-reated or require a program that is MC version-specific meaning it will not work in a previous or earlier version. Also, I want to do this as much on my own as I can, so I don't have to wait for a program to update before I can mod again. Basically, here are what I need to know how to do:

Code a hostile mob

Assign a texture for it (I know how to create a texture, just not how to get a mob to appear with that texture)

Create a model for the textures of the mob and the item dropped

Code how the mob gets aggravated and when

Code a targeting system (e.g. zombies attacking villagers/doors and the whither boss attacking everything that doesn't attack you)

Code how it attacks

Code what it drops and how it is dropped

Please PM me as to how to do this, and if I missed any hostile mob specifications (none of which I know how to do). If your system works, you will be accredited for your help when the mod is published. All help is greatly appreciated. Note that I may not know how to mod, but I do know how to crash a computer, so I do have my right to refusal.