No You would need to change at either Paris or Brussels. In Paris it is a change of station although they are quite close.
Answer 2I don't think you can get a direct train from Calais to Brussels.
Route 1: Calais to Paris Nord. Paris Est to Frankfurt.
Route 2 (which may be quicker): Calais to Lille. Lille to Brussels. Brussels to Köln (Cologne). Köln to Frankfurt.
Calais
Look to the related link below for a travel guide to Frankfurt .
About an hour and a half
You have a constant speed.
Yes, you can.
You can travel to Frankfurt by plane using the Northwest Seaport.
never
When you (or an object) travel without changing speed, then you have constant velocity (speed). This means there is no change in speed (acceleration) when you (or an object) is traveling.
10 hours
Definitely by car or bus.
it all depends on how you want to travel there.
approx. 10.30 hrs 1191km