The filename appears to be an automatically generated name, likely from a messaging platform like Telegram or a cloud storage service . Because these names are randomized, they don't refer to a specific, well-known guide or piece of media.
Download MediaInfo and drag the file into it. It will show you the video title, the date it was created, and sometimes the original source or software used to make it. AgADnAcAAmZG6VY.mkv
Use VLC Media Player (available for Windows, Mac, iOS, and Android). It can play almost any .mkv file regardless of the internal coding. Alternative: MPC-HC or IINA (for Mac). 2. Identifying the Content The filename appears to be an automatically generated