JR pass Exchange Order activation

Dear Daniel-san,

I had consulted a few local brokers in singapore and was informed the following:
Query 1. I would need to be in Japan (with my passport) to activate the Exchange Order in end-dec 2023 (after i purchased the JR pass in end-sep 2023, ie. 90days).
Query 2. I would need to top up the excess fare (for my purchase in end-sep 2023, activation of exchange order in end-dec 2023 and actual usage in mid-Jan 2024).

As I would only be in Japan on mid-Jan 2024, could you guide me how I can activate the Exchange Order in Singapore, or online?

Could you confirm whether a fare top-up is really required for Query 2?

Much appreciate your guidance.

Thank you.

Regards
Steve