Does this shampoo and extract to really deep clean (mattresses, furniture, car seats, etc.)? Or just simply steam? Even with the three modes.

Great question. The Little Green HydroSteam does shampoo and extract, not just steam. It sprays cleaning solution, uses HydroSteam to help loosen tough messes, and then extracts the dirty water, making it effective for deep cleaning items like furniture, and car seats. The three modes adjust how the solution and steam are applied, but all are designed for extraction-based cleaning.