just one question:
Will be my PIGGY balance on Poloniex converted automatically or I should withdraw the coins then go to 1:1 convertion exchange and then deposit back them to Poloniex?
it won't be converted automatically but you can do the exchange directly with poloniex addresses.
Thanks, and a second one because I'm not familiar with POS (and I wouldn't be if it wasn't the PIGGY).
Is my interest rate calculated in exchanges or the coins should be in my wallet?