Will an upgrade to an internal ssd, remove an activation lock? I bought a used iMac a1419 2013-2015 I think the owner forgot to remove it or I created one and forgot the password.

Definitely not an Activation Lock as mentioned by @Servant of Cats or you could not boot into macOS itself to provide those screenshots. If you see a padlock on the screen when trying to boot into any special startup mode, then that is a firmware password lock which can only be removed by providing the correct password, or by having the 1st owner of that device remove the firmware password lock for you by contacting Apple on your behalf which would require that person to have acceptable proof of purchase & personal ID and the special code that must be generated from the firmware lock screen by using a special key sequence.

Set a firmware password on your Mac - Apple Support

If you cannot do any of this, then you will never be able to boot into any special modes on this Mac. If the hard drive ever fails, then this Mac will be a brick. Unfortunately this is one of the dangers of purchasing a used Mac.

That's an iMac (27-inch, Late 2013). It is not an Apple Silicon Mac, or an Intel-based Mac with an Apple T2 Security Chip – so I don't think it supports Activation Lock. That was an iPhone feature before it was a Mac one.

Reference: System Requirements section of Activation Lock for Mac - Apple Support .

The owner might have set a firmware password – not just a Unix login one – and if they did, even replacing the drive might not be enough to clear that password. Firmware passwords were the old way of locking down your Mac if you didn't think that Unix login passwords and physical security were good enough.

But woe unto anyone who forgot their firmware password. You lock yourself out – you've really locked yourself out. Apple can remove firmware passwords if you are the original purchaser, and have proof of purchase documentation that is satisfactory to them, and bring the Mac to them. But that wouldn't apply here.

I believe there are ways of resetting the Unix login password, although I'm not sure if Apple's current directions are the applicable ones for such an old Mac and old version of Mac OS X.

If you forgot your Mac login password - Apple Support

That model is a late 2013 17" iMac. If the previous user didn't prepare it according to this Apple document, What to do before you sell, give away, or trade in your Mac - Apple Support, enabled a Firmware password/lock and you don't have proof of purchase w/serial no. to take into an Apple dealer along with the iMac you've got an expensive door stop on your hands.

If you can I'd take it back to the seller for a refund and get one thru a reputable reseller like OWC (MacSales.com) or an Apple refurbished model.

You can upgrade that Mac as far as Catalina, and no further.

Catalina is not recent enough to run current applications from the likes of Microsoft and Adobe. It also breaks 32-bit applications (such as games) that ran on previous versions of macOS (like High Sierra and Mojave).

It is enough to run the current versions of Firefox, LibreOffice, the GNU Image Manipulation Program (GIMP), and the commercial Affinity V2 applications (Photo V2, Designer V2, Publisher V2). Those can extend its useful life to some degree. But I think you're likely to find that most new commercial applications won't run on it.

How to download and install macOS - Apple Support

Note that A1419 is not enough to uniquely identify a particular iMac model. MacTracker indicates that Apple used that model number for six 27" iMac models released between Late 2012 and 2017 (inclusive).

The model ID "iMac14,2" (shown in one of your screen shots) is unique to the iMac (27-inch, Late 2013).

I don't know the rhyme or reason of why Apple uses non-unique model numbers and model IDs (except in a few cases where machines are practically identical), but they sometimes do …

Old Toad wrote:

If you can I'd take it back to the seller for a refund and get one thru a reputable reseller like OWC (MacSales.com) or an Apple refurbished model.

If the OP follows this advice – and wants to run modern Mac applications, I would suggest that the OP look for a Mac that will be compatible with Sequoia. Or, at the very least, one that is compatible with Ventura.

macOS Ventura is compatible with these computers - Apple Support

macOS Sonoma is compatible with these computers - Apple Support

macOS Sequoia Preview - Apple

It won't be too long before Apple releases Sequoia and the "most recent three" are (Ventura, Sonoma, Sequoia). Then you'll see Adobe, Microsoft, and the like dropping support for earlier versions of macOS like a hot potato. Ventura will have about a year before it, too, falls out of the "most recent three"; Sonoma, about two years; and Sequoia, about three. (These are educated guesses based on Apple's recent macOS release history.)

Note: An Apple Silicon Mac that can run Sequoia is likely to get several macOS updates beyond Sequoia – i.e., more than three years of support. It's just that until time passes and Apple releases those future macOS updates, nobody here can give a definitive answer to the question of how many additional updates a particular Mac will get.

If the OP is looking for a Mac to run 32-bit games, then the OP would be looking for an Intel-based Mac which is able to run something before Catalina. The overlap between Macs suitable for running 32-bit games, and those suitable for running modern applications, is growing smaller and smaller, so the OP really would need to decide what their primary objective is for their machine.