Hello Vinod
Prefix suppression commands, like any other commands, depend on the IOS being used. Because GNS uses reali IOS files, it should support any feature supported by the IOS in question. Make sure that the version you are using supports the commands you’re looking for.
According to the following link, the prefix-suppression command was untridyced to the IOS from version 12.4(15)T and was integrated into Cisco IOS XE Release 2.6.
The corresponding interface command ip ospf prefix-suppression was also introduced in the same IOS versions.
I hope this has been helpful!
Laz