Hi,
1. There are two things here:
a.You want your clients to inquiry about one product at a time. In that case, you can activate the "Display a contact button on the product page" option of the configuration (commercial editions) which will display a "contact us for more information" on the product page, display a form for the user to ask questions and then send an email to you with the name of the product and the text of the user and you will be able to reply to him.
b. You want your clients to inquiry about a cart. In that case, you would have to change your checkout workflow in the configuration of HikaShop to remove the payment view so that the checkout just create an order without any payment involved. Then, you would be notified as administrator and you could set a payment info, change the price, etc, email the user and have him pay for his order from his orders listing (there is the option "Payment of orders not paid immediately" in the configuration of the commercial editions to allow the users to do that).
2. You can have admins create orders for users on the backend and email the users his order and ask the user to pay via a link. However, they will be able to see the orders of everyone, not just theirs. And there is no commission calculation in place as orders are not affected to any "vendor" but just the user purchasing.