Hi, Concerning the decay rate, from the Wiki: The decay rate is dependent on the player's current "Internal Grade" and is shown on the table below in units of frames per point. If your displayed grade is 8 and you have a decay rate of 80, does this mean that you lose 1 Internal Grade Point for every 80 frames? Thanks
Hmm.. Sorry, I am not very well informed about the working of the decay rate, but don't worry, somebody should accurately answer you soon..
Yes, but you don't decay when a piece is not active, and also you do not decay for any piece directly following a line clear.