"select/adjust32 - does it fully support the USB on Iyonix?"
It definitely should, if it in any way pretends to be a worthwhile replacement for RO5. Imagine installing it and not being able to use the mouse, because it relies on Castle's USB stack...
"select/adjust32 - does it fully support the graphics acceleration on Iyonix?"
Again, it definitely should and in some sense it must, because the Iyonix relies on it for its display.
"RO4.40 may be OK for an A9 - but how much of the RO5 stuff will be implemented?"
Some features were already implemented in Select, like DHCP, whereas others not, like UMDA. I can only expect Select for the Iyonix to build upon the functionality already present in RO5 to offer a definite, uncompromising upgrade for existing users.