25Gb to 10Gb Downgrade
Yes:
You can downgrade a 25Gb channel to 10Gb by using 10G transceivers. This involves connecting a 10G SFP+ module to the on-board 25Gb ports for a 10Gb connection.
10Gb to 1Gb Downgrade
Yes:
You can downgrade a 10Gb channel to 1Gb by using a 10G SFP+ to RJ-45 adapter. This allows connection to 10Gb host board ports for a 1Gb connection.
FC 32G Downgrade
Partially:
You can downgrade FC 32G to 16G or 8G, but not to 4G or 2G due to chip limitations.
100Gb Downgrade
No:
Downgrading a 100Gb channel to 40Gb, 25Gb, or 10Gb is not possible due to chip limitations.