Q: Re-installing Snow Leopard to a mid-2010 Imac I3 advice?

Hi,

I've already gotten some good answers in another thread, but it had a different title, so I thought I post it here and perhaps some more members will have experience with this:

I just bought a used Imac that is currently being shipped to me.  Here are the specs: Mid- 2010 21.5 inch screen, Model A1311, Serial: W8114294DAS, Intel Core I3 3.06 ghz processor.

It will come running El Capitan, but I was advised to wipe the drive and reinstall the original operating system, which is Snow Leopard, then upgrade back from there to El Capitan, with my own Apple ID. However, it seems to be tricky with this particular model. If the computer originally came with Snow Leopard 10.6.4. my retail disc may not work for the re-install.  I was told that Apple might be able to ship me a custom-made one. I also read on yet another thread that perhaps these models came with a slightly different version of Snow Leopard, and that's why the retail CD may not work, even if the computer came with version 10.6.3. and it would be better to get a customized one. Is that true?

Then there may be an issue of a firmware update that the computer may or may not have and that could cause problems (not allow Snow Leopard to install at all, or instead install Lion). Is there any way to tell whether it had that update and perhaps disable it before attempting to erase and install Snow Leopard?

Does anyone have advice/horror stories to share before I actually attempt this? Or what would be the best way to go about it? I thought I'd try my retail SL CD first and hopefully it will work. If not, I could order the custom-made CD and try that one. If I can't erase, at least I haven't done damage, but what if I erase the disc, but then can't install Snow Leopard? I'd be left with a blank computer. Or should I be able to install it once the drive has been erased?

Someone also mentioned using SuperDuper to perhaps erase the disc that way or at least make a back-up? I haven't used that before. There wouldn't be any personal info on the computer yet, as I would attempt the re-install before anything else, so I just need a way to install El Capitan under my own Apple ID, so I will be able to install updates, or even a new operating system, as it becomes available.

Is there any danger of trying to use my retail SL CD if it lets me erase and install (like installing the "wrong" Snow Leopard version)?

Here's the link to the original thread: Buying used Imac advice?

Thanks for any insight!