[LeHobbit]

I have a couple of questions about audio formats applied to Blu-ray :

1) Is the data rate of Dolby Digital Plus and Dolby TrueHD constant or variable ?
2) Can a Dolby TrueHD be downmixed to another format like Dolby Digital ?
3) What is the maximum data rate for LPCM ? Is the data rate constant or variable ?
4) How a 7.1 LPCM soundtrack is downmixed to 5.1 or 2.0 ?

Thanks for your answers.