How does this flooring hold up in a southern exposure room that gets a lot of sunlight? Can you instal this on stairs too?

Southern exposure rooms will hold up to sunlight, however, we recommend gluing the material in that area to prevent any issues (material will handle up to 140° radiant). This can be done by using a cork compliant adhesive and a 1/16” x 1/16” notch trowel. Glue down the areas where the sunlight reaches into the room and go 2ft past to allow stability in room temperature variance from direct sunlight to indirect. The adjoining material can be simply be clicked together and float installed throughout the remaining area. This flooring is suitable for stairs, please see the appropriate moldings that we offer to properly install and finish edges of stairs, listed under "Accessories" on the product page.