2 questions, coding MMORPG in Java

Newbie & Debugging Questions
#1

Hello! First post.

  1. First of all I wanna ask you guys (I am newb, beware) if would you code a game in Java without using any game engine or thats absolutely stupid idea.

  2. Secondly, what do you think about JavaFX for gaming? I know theres libgdx but thats third party.

  3. Do you think its possible to create single player game and then change it for MMORPG? Or I will need to start from a scratch while creating MMORPG? Which way is less troublesome?

Thank you!