I am about to buy a second-hand HTC One S for development mucking around. The seller says it needs to have its firmware reset, but won't say why.
I intend to hard reset it anyway and wipe everything. Will doing this also reset the firmware, or is the firmware "lower level" than the factory default settings?
From this post:
System updates overwrite
/system. Factory reset wipes/dataand/cachebut doesn't touch/system. Simple as that.
The seller likely is just trying to eliminate personal data to prevent you from getting hold of any.
And in extreme cases where /system does get reset/cleared, there's always RUUs (HTC's factory firmware) which you can use to recover. In fact, even if the phone works just fine when it arrives, you might still need it to update the phone to the latest version available (OTA updates might've been discontinued by HTC).
Q & A