Headscratchers / Medabots: Metabee and Rokusho

• After completing the normal and post-game. There are four mysteries that are still unsolved till this day:
  • The mysterious Rubberobo in the Ninja Village who you can't talk to and stands in front of a house which makes you unable to look inside of it as well.
  • Where Hachiro is on Medabot Island and is it possible to contact him again?
  • What Rintaro is doing on Medabot Island and if he has any significance or is just an easter egg for the anime viewers?
  • What's outside the mysterious house which you enter through the vending machine?