1) Searching in "File and Folder names" only will display results foun in file metadata:
2) Search with Russian words will display irrelevant results:
2.1) box finds particular letters, not complete words
2.2) box displays search results even there is no file with requested name
Nick Chokas commented
Ditto - Same experience. Would be nice if Box would add Russian to their list of supported languages for Search Indexing.