It is next to impossible for you to brick your calc without unlocking flash and some other advanced stuff.
The worst that can happen is a RAM clear.

Under normal use, the flash (archive) cannot be edited. While the OS has access to the functions and privileges to write to flash, it requires some very specific exploits to unlock it for user use. The possibility of accidentally unlocking flash is astronomically low.

So in other words, you may erase RAM frequently, Flash+RAM (very infrequently, even when I was putting in semi-random stuff I never had the problem), and I think that unless you somehow unlock flash, it's impossible to brick your calc with code.

well, everything in ramsould be gone on a RAM clear, so nope.

You would have to be , as mentioned, extremely unlucky to experience anything other then ram clears/freezing. Which is nothing a battery pull wont fix. Once you start messing with changing execution permissions you may have some issues due to changing them requires execution from a privileged page which required unlocking flash to get the ability to write whats needed, and if the routine you were using handled that bad you could see issues. Shy of that, if your not playing with flash unlocks you could break your screen with test mode?!? Other then that yeah only thing that could be lost is the contents of ram. Your archive would remain safe.