Is Libre Office backwards and forwards compatible with Microsoft Office?
what is “backwards and forwards”? what aspect of operation of LibreOffice and Microsoft Office are you talking about? macros? command line interface? API? file compatibility? automation? applications included? UI similarity (training cost of migration)?
Compatibility implies translation of concepts when an application opens a foreign file. Keep this saying in your mind: Tradutore, tradittore! and always expect problems in not-so-corner cases. 100% compatibility cannot be guaranteed unless you use the original application (and even in this case, when versions are updated …). Fortunately, common files behave quite well, but keep an eye on the results.