I - Can anyone with good experience with Quest if app inform me how the program handles branching stories and multiple options in conversation lines. ? I have been through the tutorial but i could not find it out.

II - Any idea of which IF app is good for branching stories & conversations with RPG elements such as "action/combat system" and other variables ? obs: I have nearly zero coding skills.

Hello!

Quest was made for doing it, so don't worry. It will handle any parser adventure or Gamebook you have in mind.

For adding combat and RPG style elements, you need some programming. The Forums has some ready to use solutions for many's cases. It's just research a little and practice.