By end of this year i’ve read…
Also by the end of 2017
Not soon I think. They’re struggling hard since Metal.
Now as Metal is launched and lounges can be selected where can i find the rules for those lounges?
You can ask the lounges directly 
Actually you need to book (and pay from the second booking on - if Metal) the lounges from the app. You will be prompted to choose which lounge during the booking process.
imho the price for booking lounges should be lowered for metal users, as it’s the same for the premium subscription