Dual boot TO4 from mSATA SSD?

I have flashed openwrt18.06 at the internal flash of my omnia and it is working good for a year now. I have an mSATA SSD 128G installed on the router.

I want to test TO4 and I see there are relevant instructions here

I am wondering if I can flash TO4 at the mSATA SSD (which i will format btrfs) and be able to dual boot.

If this is possible, I am also wondering if I will be able to dual boot remotely (uboot-envtools are available in openwrt).
I will appreciate any guidance.

That is possible with configuring and applying the respective u-boot environment settings as described in documentation as well as extensively discussed in this forum.

that is also possible via ssh, been discussed in this forum