PC user with SEVERE iMac failure problems

[CerntennialMan]

I am attempting to help my adoptive daughter with her 2015 21" iMac after her abusive boyfriend seems to have erased the hard disk..and from all outward indications it seems there is no MacOS available, or so I believe (certainly cannot boot). As the title implies, I am more PC knowledgeable and have very limited exposure to Apple PCs and Apple OS, but I'm hoping some kind soul might step me through how to: 1.) verify that the hard disk is fully functional 2.) restore the primary partition and OS since it appears from the recovery tools (obtained by holding down Command key and R key from initial boot) that this is what he has done: deleted the primary OS partition (since within Mac Utilities and Disk Utilities there is only one partition apparent, labeled: "OS X Base System" to be found in a 2 GB partition - 724.3 MB available). At the top of this window is what I perceive to be the Apple HDD, a Hitachi 1 TB HDD (HTS541010A9E62 Media), but from what I understand there should be a partition for the MacOS in , and my thought is he has deleted and altered the partition type which appears in Disk Utilities to be 'unknown' and 'unformatted'. So how can I retrieve and re-install the MacOS ..? From info I found online at Mac Rumors and Everymac.com, this OS version was probably originally MacOS 12 - Monterrey). Being as foreign to MacOS as I am, I'm asking some kind soul for a bit of "hand holding" in how to get this PC back for my daughter, insofar as it SEEMS to be operational, but even in this I could be mistaken.

 

[Tech Support Otter]

Since this is a 2015 iMac model, you will be following some steps for the older Intel-based Mac's.

Use macOS Recovery on an Intel-based Mac

Learn how to use macOS Recovery on an Intel-based Mac.

support.apple.com

If an Intel-based Mac is unable to start up from the built-in Recovery system (Command-R), use this command to start up from macOS Recovery over the internet to reinstall the version of macOS that came with your Mac or the closest version that’s still available:

Shift-Option-Command-R


Let me know if you are able to progress from here.

 

[CerntennialMan]

Well THIS was an endeavor...!! Lotsa horsin' around trying to reinstall macOS Sierra by using the 'normal' access to Internet Recovery (Command-R) only to finally find out that this iMac had been upgraded to Monterey, so access to this recovery was only available to me via Option-Command-R, which gained me access the macOS Monterey Internet Recovery... and after then finding out I had to change partition types (yet again), I finally got Monterey installed and working. Only took me about 6 hours TODAY (saying nothing about yesterday's efforts..) to 'fight my way through" several confusing situations and a LOT of time (>3 hours) waiting for it to complete and begin allowing me to set up her account (which meant, of course, that she had all her login info on a damned pieced of notebook paper.. which has now changed). But success is sweet and she is happy - and I am happier still that this 'troglodite' is gone from her life... And back in jail.
Thanks Otter... I owe you one...

 

[BrianBaughn]

Six hours isn't bad…considering all the factors there.

 

[CerntennialMan]

As I did more research, it would appear you are right ... "From scratch" installation on what was in essence, a totally erased HDD (?). If it didn't have what was shown as 7235 hours on it I might even refer to it as 'new'. But this was also because I did a 'security erase' on that partition which took roughly about 20 (+/-) hours...
But it wasn't working anyway, so.. WTH (?). And as a retired 'nerd' I've got nothing much else to do, anyway...
But in knowing this -uh - (😠... and I will attempt to control myself here..) 'less than savory individual', I wanted to make very certain there wasn't a trace of anything left on this disk. Probably added some time to the situation, no doubt..

 

[gilby101]

As an aside, is your adoptive daughter taking steps to protect her online identity and passwords? An erased disk might the least of her problems.

 

[Fishrrman]

Agree with gilby.
She ought to consider changing her address, as well.

 

[CerntennialMan]

We had that discussion yesterday when I brought this iMac back to her... A fairly SERIOUS discussion, BTW (old fart veterans, like me, can be a bit "vociferous", y'know...), and we then signed her up for an entirely new email address, and (being the old dude that I am..) also had serious discussions regarding ALL 'social media' considerations (since I think these are the absolute bane of society nowadays), but "kids will be kids" and I'm 'old' and she is 'young' and I have to allow that she is her own person, despite how I might perceive her. Never thought I'd wind up being a 'dad', but here I am, trying to do the best I can, and I have to let her make her own decisions.... and her own mistakes.
Tough as I might see that to be...