I think this condition is on that particular flight ticket type only.  Since the agent has accepted such conditions from airlines, then same condition will be applied to all members by auto

If flight ticket conditions is as per my assumption, agent should let tour member know.  But not many ppl will join this tour since it is not under their control.
If you are not inform, then you need to proof the conditions is not available or you not been informed.
For insurance, depend on the policy.  If the case can support, you can claim.