Yes Solex TV works in Firestick, please click here to check youtube tutorial how to install Solex TV in firestick
Currently Solex TV doesn't provide Subtitle but you can get by using external player such as Mx Player or PlayerXtreme Media Player
No, Solex TV doesn't provide live streaming
No, Solex TV doesn't allow downloading
SolexTV club is a paid membership where you will get first priority for Movie request, Tv series and lots more. Currently it is invite only.