Here is the thing, ICX has 2 flash partitions primary and secondary. You can load Routing or switching code to any of the partition based on your requirement. Starting from FI 08.0.90 we have introduced UFI image, i.e. A unified FastIron Image (UFI), consisting of the application image, the boot code image and the signature file, can be downloaded in a single file. Beginning with FastIron 08.0.90, there will be primary and secondary partitions for the boot image and new commands have been introduced along with other changes. Its not a recommendation to have a pre-08.0.90 release in one partition and FI 08.0.90 or later in the other partition, Pls go thru 'Ruckus FastIron Software Upgrade Guide, 08.0.90 for additional info.
You can use boot system flash primary/secondary to switch between the partitions.