... thanks for this week's "wow I am old" moment.
Itunes was originally something for music, however it managed ipods and later iphones as far as getting data to/from them (officially it was the only way as well but other options did exist). The iphone4 family still being within that paradigm but did do over the air updates and the like so it was mostly a convenience and means of doing backups for most people. Said backups would include a factory reset though.
You will want the pin code at least though if going this method.
If it is files from them then do check if there are old laptops that might have backed things up and just been stored rather than flattened and sold on. That might have pictures to at least the last backup (and it was fairly automated/something it bugged you to do rather than relying on tech illiterates to make the "everybody forgets to back up once" mistake) which could be something in this, and they will be simple files within the itunes directory (indeed such things were the primary cause of full hard drive in those timeframes -- they might only be a few gigs but when the average laptop of the era would be good to have 80 gigs then several backups of a full phone or indeed two or three if family usage nails that quickly enough).
In most cases though you will want the password, or associated icloud account* to bypass protections if doing it the "proper" way -- no point in having none or someone could steal the phone, plug it into a random computer and copy files off as a slightly more annoying USB drive.
I am not sure what has been achieved on the hacker side of things here (I think we might be beyond baseband unlock for this but I have not kept up with iphone jailbreaking and hacking for the older stuff) as that might be able to bypass things as well. A casual scan says there are some things available depending upon the IOS update it is on but at this point I am copy-pasting one of those and don't have a 4s here to test with.
https://www.coolmuster.com/unlock-iphone/remove-activation-lock-without-previous-owner.html looks like a reasonable start, but I have no experience with them.
*if someone sent an email from their iphone in that timeframe (to themselves, to some relative that keeps old emails, to a friend...) then it might include the icloud ID associated with it as a lot of phones would default to the apple email service.