Will my customer see whether a hotel room can be cancelled for free, and by what date, before they pay?

Yes. The cancellation terms travel with the room rate itself, so every room in your search results carries its own policy, either free cancellation up to a certain date and time or non refundable from the moment it is booked. Your portal can show that on the room card, and again on the checkout page, so the customer reads and accepts it before paying rather than finding out afterwards.

How much detail appears depends on the supplier. Most send a clear deadline and the charge that applies once it passes. Some send only a short line of text in their own wording, and a few give the deadline in the hotel's local time rather than your customer's, which can confuse someone booking from another country. Your portal can only display what the supplier sends, so it is worth looking at a few sample rooms from each supplier you connect and seeing how readable the wording really is.

One thing that catches agents out is that these deadlines move. The free cancellation date is usually counted back from the check in date, so a room that is refundable today can quietly become non refundable a few weeks later without anyone changing anything. The safest habit is to save the policy against the booking at the moment it is made and print it on the voucher, so you and your customer both have the terms that applied on the day.

Before you go live, run a test search and compare a refundable room with a non refundable one, then follow the wording all the way through to the confirmation email and the voucher to be sure nothing is lost along the way.