Any hope for the little guy plus new additions (Pic heavy)

My grandma has been moved into a home so I got to score some cactus that she had along her side fence.
They are actually my uncles but he's in hospital at the moment (motorbike accident) so I've got the cactus. I don't know whether I'll have them permanently or if he wants them back but he hasn't done anything with them for the 20 years that he has left them at his mum's place (my grandma). The past week at grandma's place they have been subject to frosts and haven't had dry soil in weeks. Not a good combination!

I need some help identifying them. I know ones a mamm. There's too many mamms to work out which one it is. I think the columnar cactus is Oreocereus Leucotrichus. And I guess there's two echinocactus (grusonii?) and some other. I've got no clue what the last one is.

There was originally 4 mamms. in the pot but when I got them one had totally rotted away and the smallest one had rotted too. I don't know if there is hope for it or not. I don't know what inside the rotted mamm. they look like roots but they wouldn't be I don't think. I pulled off the rotted part and that's what it looked like underneath.









Oreocereus Leucotrichus?


near the top of the image there is a fissure in the plant and it divides the old looking growth (not hairy, areolas that aren't producing fresh spines and a calloused epidermis) from the fresh looking growth (hairy, green and all the areolas are producing new spines)




E.Grusonii?


Other echinocactus


Unkown cactus

Areolas and spines of Oreocereus:

Below fissure but above callous


Calloused area


Above fissure


I just found a hole in the side in the un-identified cactus it goes through to about half way


And on the other side of the hole the cactus is sunburnt.

I want to dehead it even though I don't know if I get to keep the cactus or not.
Should I dehead it and what season should I dehead it in.

Thanks. Mitch.

Don't think there's any hope for that first mammillaria unfortunately, looks like M. hahniana btw.
And I don't think that second Echinocactus is Echinocactus, look more like Parodia sellowii.

Thanks for the I.Ds.
Parodia sellowii has so many synonyms! 30+!
Should I put the rotted M.Hahniana in soil now because its pretty much calloused

I've decided to cut the head of the cactus with the hole in it (Notocactus?)
To cut above the hole I only get about 5cm of cactus. Is there any problem in taking a cutting from this cactus of only 5cm.
I could grow it this growing season and cut off a more sizeable cutting next year if that would be any better.
I've never taking a cutting from a large cactus before.

Nice pics

Blame the camera for the good pics not me
Winter sucks. All the plants go to sleep!

I would wait and see if it grows any when things warm up. If it doesn't, then I would cut it. If it grows, I'd wait a year or so till I chopped it.

Thanks IXOXI. That's what I have decided to do.

What do people think of the I.D of notocactus scopa for the cactus? Someone else suggested it, it seems quiet plausible to me but it's hard tell because of its growth.

I can take a look at mine and compare it with the photos, later this evening.

Would be much appreciated IXOXI. I don't know why I thought the other one was O.leucotrichus... It would most likely be O. celsianus