Performance Data Question

I am inputting the data for a citation. What do I enter in the form for areas where the aircraft no data in the POH? I’m referring to high altitudes, temperatures, and weights where the airplane can not stay there and has no numbers. Do I leave those boxes blank or do I enter zeros?

Leave the high altitude/high weight/high temperature corner blank if you have no data. Do not enter zeroes.

What is the reason for using TAS on the cruise preformance chart and IAS on the climb and decent?

I gathered information for all of my numbers by TAS. Should I just go though the prosess of converting them or is this a typo?