I cant get a transparent dock on iphone...and the background on opening the folders and control centre is not transparent too....how do i change this grey to transparent

The dock hasn't been transparent in a long time, however you do have the option to clear it some. Go to Settings>General>Accessibility>Increase Contrast, and you can turn off Reduce Transparency. You can also go to Settings>Display & Brightness and to my knowledge it needs to be set to Standard instead of Zoomed.