How to make reservations for orders created with order import.

Could you please tell me how to reserve the backlog (to be received) for multiple orders at once when importing orders?

Is there anything to consider when making reservations for backorders (scheduled for receipt) instead of on-hand inventory (available inventory) when receiving orders?

① When making a reservation when receiving an order, is there a difference in the procedure for making reservations for inventory and for reservations for backorders (scheduled to be received)?

② Is there a way to make reservations for multiple orders at once?