@baloouriza Currently #AndStatus uses Android's native way to handle the stack of activities thus allowing a user to move backwards just like in any other Android app. Changing this would surprise a user...
I think that what you really want is that a Timeline in the stack would be automatically updated and re-positioned to the latest viewed position on its opening during the User's navigation "back" - currently a Tímeline from the backstack usually shows outdated information.
?!
Please note that navigation to the Default Tímeline currently clears the whole activities stack thus allowing you to return to the beginning in one tap. I usually do this exactly to avoid long return using the Android stack.
Just set the Default Tímeline properly...