1) You only need one amiibo ( the 9 compatible ones ) to unlock this game mode?

2) Once you unlocked it, you only need 1 amiibo to play 4 players in amiibo party? 

3)  If you only have the mario amiibo, would the gameboard still change ( like one section could turn into a yoshi one ) ? Or to have this effect, you need another amiibo? 

I have only seen other people play it on YouTube but I'll try my best to help:

1. Yes even a bowser amiibo works
2. Not sure
3. Yes. While you play you pick up these tokens and those tokens allow you to change one section of the board to the corresponding character that is on that token ( i.e. If you pick up a DK token you can change a section to the DK board)

Hope this helps!

Yes for all 3 questions.

^ This

OH! Thanks Guys!!!!!
Because im buying this tomorrow, and it looks like i have to buy the bundle! ( only have kirby )