You mean that tall button that only goes down halfway? Grab onto a Floro Cragnien nearby and stand on the switch while holding them. That'll do it.
Chapter 4.
It's Chapter 1.
It's in Chapter 7.
Chapter 1-1
You will "find" him after chapter 6.
By getting dottie
Easy just ride the boat
It is 5963
go to bestouvise in chapter 1-1
It is 5963
in chapter 7-1
As sap soup is only available in Super Paper Mario, you get it sometimes when you defeat Floro Sapiens in chapter 5.