Re: Open BIOS?
Since ARM systems come from a whole different ecosystem, one based on memory maps and fixed hardware designs, basic operations and enumerated buses are likely to be approached from a whole other angle, one that may see something completely different from a BIOS like x86 does. After all, PC-based Macs didn't have to wrestle with that kind of stuff and went straight to EFI, just to name an example.
Having said that, you can't be sure there isn't some kind of uber-root mode hidden in ANY kind of system, regardless of the architecture. Indeed, they may reside in an even lower level than that: say in the network chips.