I have an old medicine cabinet with cracking paint. I would like to repaint part, but I want it to crack. How can I make this happen?…thank you

I often see pictures of rooms painted with different colors on different walls. I would like to use a dark, rich red color in a basement room but only want one or two walls this color. I would think all the walls this color would make it too dark or

We normally paint stairs by the tread and risers and hand rail and newels separately , now a new builder want a linear foot price??

I don’t have enough primer to cover my area for the first coat. If I were to add some paint to the primer will it still work as a primer? I’m painting over orange paint.