1) I managed to change the desktop picture when starting, but also want to change the picture when logging in (password page); it appears I'm supposed to have Build 14291 in order to do that (I have 10586.164). How can I upgrade to 14291?

2) When I click the Window icon on the start bar, there are 3 squares (This PC; Settings; DVD Drive). They are yellow (my choice) but the text is white and hard to read. How do I make it black? At the same time, my regular desktop picture shows very dark, without any icons. By the same token, occasionally, some of the text on white background is yellow - also hard to read. could I make all text black, unless it's on black background (like on the Start Bar), in which case I want it white - as it actually is now.