1) How to reproduce?
2) Search/replace is current file only (ever if global). "Find in files" has a replace across several files.
3) Global, for the current file. Make sure to also change the origin to "begin of text" or to "wrap around"
Rename Identifier is a different behaviour.
Say you have a variable FFoo in 2 different classes. Rename Identifier will work out to which class each occurrence of FFoo belongs, and only replaces those that belong to the class you selected (when starting rename identifier). So it is a "smart" replace.