Product photos

Good afternoon I have a few questions about the product photo: 1. Background We want to upload photos without background into the box and then upload them to OpenCart, but the box adds a white background. Can this be fixed? 2. Dimensions Does boxing distort the size of the picture? Let’s say if we upload 800x800, 1500x1500, 2500x2500, will they stay like that if we upload them to the site, or are there restrictions? 3. Format We upload a PNG photo, and when you download it, the format becomes JPG. PNG not supported? Is it possible to make PNG supported? Does box support webp? 4. Quality Does boxing reduce quality when transferring photos to OpenCart?