Will a cat clean himself no matter how young he was when abandoned?

Sure, cats are naturally fastidious groomers. Their mothers clean them and stimulate them to go to the bathroom when very young but they will naturally groom themselves as they mature. A cat the stops grooming itself is usually a sick cat.

So a cat will groom himself not a bit less if abandoned at a week old?

Aside from being very old or very sick I’ve never seen a cat who was not meticulous about grooming themselves, regardless of how long the cat spent with its mother. Grooming doesn’t appear to be learned, but rather an instinctual behavior in cats.

I have seen cats which were non groomers. Usually they have been feral. I adopted a found kitten once which did not groom on its own. It was easy to get it started though. I just got some tshirt rags, dampenedthem slightly, and grommed him with those. He soon started picking up the idea and began self grooming.

Agreed. Aside from ones that are really old and having issues, all cats will groom themselves if they live with people. Feral and some homeless cats, not necessarily.

Even feral/homeless cats will groom themselves to whatever extent they can, they just might not get a lot of opportunity to.

^ and…feral/homeless cats always look dirty most of the time because they are under cars, lying in the streets, dirt, etc. A house cat lives in a cleaner environment so they look cleaner.
Doesn’t mean they don’t groom themselves but if they have been on the streets for any length of time they are just going to look permanently scruffy and dirty regardless of how much they may groom.

I knew one homeless cat who would roll in dry dirt. Maybe he was trying to eradicate fleas? He had a lot of white fur but was always quite thick with dirt when I saw him.

I’m also thinking of the outdoor cat colony cats I’ve seen.

Of course, I also just saw my own cat with an extra layer of dirt. Hopefully he’ll clean that off outside…