Every time I open SM with mobile devices there is a golden box, but after the first time I clicked it, error occurs with the above words.
That happens everyday, you login on Mobil. Though, you get to open the box once a week. So, every day you will see the box appear on Mobil device. The box will appear every day, yet you get to open it once every seven days. So know which day you get to open it.
What is this, is this for android only?
Yes it is. You have to log in with your phone on the supermech ap.