realgaga

I'm not sure what you're trying to say here, 'Business Comfort' isn't a fare class nor does it form the fare basis. It is simply a grouping of different RBDs.
Fare basis - which is on the ticket - forms the fare rules, such as min/max stay and pricing.

You can ask the agent for the fare difference for the new date/routing then decide whether to go ahead for a change, or wait if you think one of the sectors will get cancelled.