BuddyPress.org

1 – manually, you have to rearrange the list order in header.php

how to do that ?

if you use 1.2 inspire you with this:

https://buddypress.org/forums/topic/bp-12-how-to-add-a-custom-tab-on-the-home-activity-section

3 – yes, and on each individual blog page too or by typing “wp-admin” at the end of your url: hxxp://exemple.com/wp-admin