Switch – HP 2920 switch – clear all memory

I'm aware that HP 2920 switches have volatile and non-volatile memory. I've read parts of the manual and have found commands to erase the current custom default configuration, to erase the custom default configuration, and to erase all memory and zeroize the flash. The goal is to take a fully configured switch with lots of application-specific information and to clear all the data out to return it to its original, factory-default state. I've come up with the following steps and wanted to know (a) whether this is sufficient and (b) whether this is necessary to remove all non-factory-default data and settings from the switch:

1. Erase current startup config using, e.g., erase-startup-config.
2. Erase default startup config using, e.g., erase-default-config.
3. Erase and zeroize all user data, e.g., erase all zeroize.
4. Press Clear + Reset to reset the configs
5. Remove power to clear out the volatile memory (sufficient for our purposes)

In particular:

1. If you do step 4, do you need to do steps 1 and 2?
2. If you do step 3, do you need to do steps 1 and 2?
3. If all the steps are done exactly as outlined, are the contents of switch memory distinguishable from the contents of a factory default switch – i.e., at they different from the contents before you turned it on for the first time? (I mean, in known, deterministic ways. It seems clear to me that there might be lots of random differences that are uninteresting).

I think the answer to 3. might be that if you have updated the software, then the updates remain installed, but I think that is OK for our case. Are there any other issues?

Edit: For bonus points, is there some command/action I can take whose express purpose is to actually zeroize the whole non-volatile memory, including software and configs in addition to user data, and then some procedure for putting the factory image back onto it? Is this typical? Time to perform the procedure is less important than ease/simplicity.