1&4 are the same, 2&3 will be the same!!!!
You already know how to calculate the power supplied..you stated the formula..
kVa = kW = W. ie: 2kVa = 2kW = 2000W = 2kW/hr = 2000W/hr
The peak demand of the installation will be the point in time when the installation will be subjected to the maxmimum possible loading, usually whn all electrical equipment attached to it is turned on initially. This will also be your Peak Usage.
The only way to calculate the Peak Demand is to calculate the loading of the installtion and then take into account start-up times for given equipment, when you find that you have identified a time in the day or week that has the most equipment start-ups, that will be the peak demand time, simply add it all together and convert into kW. This should also give you the peak usuage at the same time, although onlgoing electronic measurement is the best way to determine if the two do actually coincide or whether some other factor is causing a slight discrepancy..unlikely, but can happen for very brief periods.