Restriction administrator access to the user mailbox on ECP page, another user menu.

Hi guys,

Could you please help with this mater, I have dug a lot tasks but still have not been found.

When I try to set MailboxPermission to my mailbox to avoid access from administrator of my domain  in Exchange 2013 but  it is not effect, the Deny value at the description below is still TRUE, I want it FALSE but no hope.

Second thing is when I set delegation to my mailbox and access to ECP, I can access to another user when navigate to the point at the right corner on the top of the bar  in ECP Exchange 2013 page, the little rectangle button near Administrator menu, it drop down a box so I can access to another user mailbox. But when I go to the user mailbox it lead me to the user's ECP page and in this page I can go to the My Mail menu regularly, but that menu is not come up so I cannot get it drop down. I want it appear so I don't know hot to do. 

Thanks you.