@Ricardo457 Anything you change in your settings or policies or even your amenities only pertains to future bookings. Confirmed reservations are subject to whatever was in place when the guest booked.
So as others have said, a host always has the option to authorize a refund, regardless of the cancellatiion policy. Then Airbnb just refunds the guest and you don't get a payout.
But what you never want to do is use the resolution center to "Send money" to a guest for a refund unless you have actually gotten paid for that booking. Some hosts have gotten screwed doing that when the scammer guests then begged Airbnb for a refund and got it. So the guest got refunded twice and the host was out of pocket the cost of the booking.