Not understanding DNC tooltips

[Seraphor]

So first of all, the 50% procs.
Lets say I used both Cascade and Fountain, and procced both Reverse Cascade and Fountainfall.
Could I then execute them both? Or would I lose a proc?
Could I use Reverse cascade immediately after Cascade, and still combo into Fountain? Or would using a proc interrupt the combo?

Secondly, Fourfold feathers.
Do you only need one feather to use a Fan Dance skill, or all four?
Do they consume a feather?