I'm not entirely sure what you are saying here. Do you mean to say that you are unable to boot from USB running R81.10SP ISO, but you are capable of booting using the same USB running R80.20SP ISO?
Normally the issue of not being able to boot a Check Point ISO from USB is due to the memory stick being incompatible. The rule of thumb tends to be that the older the memory stick the better. Check Point appliances tends to not like USB3.X memory sticks and they prefer memory sticks that emulate as removable device and not fixed disk. Pretty much all memory sticks manufactured after 2012 is emulating as fixed disk as this is a requirement for Microsoft's "Windows-2-Go" feature.
MHO 140 should be capable of booting the R81.10SP ISO no problem. I would try other memory sticks and make sure that you are using the latest build of the Check Point Isomorphic tool when creating the bootable memory stick.
With that said an orchestrator running R80.20SP will be capable of handling SGM's running R81SP as long as you have at least R80.20SP Jumbo Hotfix 295. You could also patch your orchestrator to Take 314 or higher, then you will be able to do an upgrade from R80.20SP to R81.10SP without the need of using USB/ISO.
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