Is iControl 10.x suitable for BIG-IP v9 ??

The iControl libraries are built to the best of our abilities to be backward compatible with previous versions. For 99.99% of the methods, they will all work fine moving backwards. We actually encourage you all to update to the latest libraries in the case you get a newer version you need to access. One issue with using an older library to access a newer system is in the case of enumeration additions. If a new value is added to an enumeration that is being returned, if the client library doesn't know about it, that can cause serialization problems. The main issue with moving backwards, as mentioned above, is the risk of calling a method that doesn't exist on the earlier version. In this case, you'll get a method not found exception.