Hi,
In RUT 2xx and 9xx, both power source are connected in parallel, so if you are using PSU with different voltage it will put load on the 'weaker' PSU. It will not break the router, but most likely it will break the 'weaker' power source.
(FYI This limitation is removed in RUTX series)
You could check the device status in status>device. If the version number is smaller than HW revision 0007 and batch number 0010, then it will not support POE.