To get the B-UN hover board(where the fuck are you guys getting grandpa?) you have to beat Tanasinn. It's not very usefull, however, as you can't take in into certain areas, although it allowed me to beat the giant grandpa to the left of the starting area.

As for the clone, once you beat him you get his super-shooter. This will allow you to beat the tornado-shooting fan guy, although I haven't defeated him yet. Also, once you beat the clone, if you go right you will encounter a shift-JIS Mario castle complete with flag that, if you touch, will kill you, so either avoid that area completely or save and then go back.