B-20 changes

I thank you for efforts on Cesium.
I discovered Cesium in b-13 and with the b-20 I changed the mean to process CZML (using CZMLDataSource). The intervals in my CZML are defined with ISO 8601 datetimes. So I don't need to defined a member "epoch" for each property that uses intervals defined with ISO 8601. That was right in b-19, not in b-20. I found in Cesium source the function "processPositionProperty(object, propertyName, packetData, constrainedInterval, sourceUri)" where the next line is written:
"property.addSamplesPackedArray(unwrappedInterval, JulianDate.fromIso8601(packetData.epoch));"

Does it mean that epoch is a mandatory fo any intervals?

Like I said, my first Cesium applications were written with b-13. I updated these with your new contributions (adding sun, etc.). I tried to use the viewer but I am not able to display it in a canvas (no error in debugger and the net tracker indicates that images are downloaded by the viewer...).
My questions:
- What are the stages to display the viewer in a canvas or a div?
- I saw in the demonstrations that the sun's position changes with time, How can I make it without viewer?
- How can I define inertial or fixed frame to show trajectories (from CZML)?

Best regards