Winform Child form

Question

I made my first Child (I mean Form. Actually I am a grandfather...)
I have two problems:
1. The Child form is dipslayed on top of the Main Form, but under the main form's controls (TextBox, Buttons, etc).
(I naturally set the Child to TopMost=True, the main form to TopMost=false).
Changing the controls order to back did not help.

2. As soon as I defined the Main Form as a MDI container, its background color changed from the standard Control grey into dark grey. I can not change it back.

Both issues seem to be matter of settings, but which?
Thaks
Sam