How is current FC menu item decided & selected ?

The order in which Joomla menu items are selected and activated is

for item view:
1. menu item pointing to current FC item
2. menu item pointing to current (set in URL) category of FC item
3. menu item pointing to any category FC item
4. current menu item or the default menu item configured in global configuration

for category/tags view

1. menu item pointing to current category
2. menu item pointing to a directory view which use as ROOT, the parent category of current category (v2.1.3+)
3. current menu item or the default menu item configured in global configurationfor

for tags view

1. menu item pointing to current tag
2. current menu item or the default menu item configured in global configurationfor

other FLEXIcontent views
1. any menu item pointing to directory/search view
2. current menu item or the default menu item configured in global configuration