Mib2 boot loop and SOS emergency call service required

Hello,

the bolero infotainment system in octavia3 FL 2017 has gone into a continuous boot loop and I have a warning in the cluster of sos emergency call service required.
When checking with VCDS it seems emergency call incl. antenna works but it can not mute audio since infotainment does not work. Already checked all fuses, removed battery terminals, cleared dtcs, pushed emergency call button and aborted call.
I want to try firmware update to see if it can fix the boot loop issue but have a few questions to reduce risk of bricking main unit:

I think regular software update with enable developer mode in VCDS -> SDcard does not work since mib never finishes boot, or is it worth trying?

Is emergency software recovery with putty/rx/tx connection best chance for reinstall of SW? Is it needed SD card with firmware or does Mib2 have backup installed internally?

What happens with FeC/SwaP, coding, CP and language if I use SW train from mibsolution.one?

It is stock unit 5Q0035840B with HW H30 and SW 0363.