sstl2，sstl3 ？

when i use the EP1C6, i can set the pins SSTL3 ，

but when the FPGA which is replaced by the ep3c5 ， the the code is not changed ，then i find the pins have not the SSTL3 ,

so i have questions is that

1 : why the sstl-3 class2 is in ep1c6,and the ep3c5 have not it ?

2 :when i use the ep3c5 ,how i set the pin to instead of sstl-3 class2 ?

3: when i use the 3p3c5,and set one of bank SSTL-2, then

the

1) (IO vref ) of the bank is seted 2.5v ? or 3.3V? or not set ?

2) vccio of the bank is seted 2.5v ? or 3.3V? or not set ?

thank you very much