Well, I started playing on Beta v6 HR/RS 7 world on my desktop computer. I never saw a world-selection window until few days ago when I installed iPhone app. I logged in with my existing username and password but I was (and am still) able to select only world 175 on iPhone. After that I can see world selection window and I can select world 175, 177 or Beta v6 HR/RS 7 on desktop, but only 175 on iPhone.