Let the Installer do its thing. Its normal that it appears to be "Frozen". The Install Process can take up to 10 Minutes. If the Launcher Installation doesnt work then try this. And you need the Game-Version 4.2.0 for the Modification to work! Any older Gameversion isnt supported!
EM 5 is the base version. EM 2016/2017/20 have extra content (somewhat DLC like). All Versions work with BFENG as long as the game is updated to the game-bersion 4.2.0. Emergency 5/2016/2017 doesnt get sold anymore so you only can get some old keys or EM20. Modding EM 5 isnt that particular harder then modding for EM4. It just has a bigger hurdle to get into and needs longer time to work into. Especially with the unfortunate lack of english documentation.