5. At earlier stages, what can I do to evaluate the tentative costs I might need to pay for the other party if I lose the case? Do the parties need to tell each other about their legal costs from time to time?

5. At earlier stages, what can I do to evaluate the tentative costs I might need to pay for the other party if I lose the case? Do the parties need to tell each other about their legal costs from time to time?

You can try to make enquiry with the opposite party by way of without prejudice letter as to the qualification of his claim of costs in the course of negotiation of settlement.  However, unless otherwise directed by the Court in a specific case, there is no obligation for the litigants in a general civil action to disclose their legal costs incurred to the other party.