Files from newer versions are not and have never been backwards compatible. What needs to happen is an update of the Hand Puppet Tool and other Python plugins.
I don't know if there is already a Feedback Tracker request pointing out as bug that the Hand Puppet Tool is not working in IC8.
Unfortunately, RL has not been very forthcoming as to when the Python plugins will be updated. As RL is listed as the author they cannot blame it on laxness of other developers.
For now, you could create your animation in iClone 7, save at as a motion and then use it iClone 8.