Oh of course silly me - I was forgetting that old style one they had that was tiny and awful!
For a transition day I usually just let them have a play and an explore in the new cage. So it won’t be fully set up as his old cage will still be set up.
So you just put bedding in and obviously it’ll have its own wheel so that would be in, and maybe put one favourite tunnel eg in from his current cage (which you put back again afterwards). And any other new items you were planning to use (if any). Sprinkle or hide a few treats or bits of food for him to find.
So basically it’s a bit of playtime in it but it’s not fully set up. You could fill the base with new substrate and then at move over time move most of his existing substrate on top of it and press it down.
I’d give him a reasonably good period of time in it which is why he needs things to do in there / foraging, wheeling or exploring a new item. Maybe an hour but if he shows he wants out before that then don’t leave him in or he could get stressed. I’d also stay and talk to him while he’s in it but I’m sure you do anyway.
Then he just goes back to his current cage as before - the on e familiar item you’ve taken out, you out back where it was before too.
Next day you do the move over. Obviously Socks would need to go in his pet carrier somewhere.
Socks will have akready part scent marked some things in the new cage after his play time in it, which is what helps them adjust much quicker and it be less stressful and already a familiar place.
You’ll already have bedding and a wheel on there. So then just move everything over from his current cage - spread the old bedding on top of the new and RESIST the temptation to spot cheap anything - he needs his old familiar smells very much at changeover time.
Try to keep the layout the same as before - eg if the house was on the left have it in the left again. Any smaller familiar items in the same location. This really helps them settle if their “route” is exactly the same- then the only thing that seems different is the walls of the cage itself which will be curious to him rather than scary - as long as everything else inside is the same and same layout. Even a half chewed chew - just move it across anyway.
I know you mentioned maybe having a sloping deeper end - I woukd leave that until later as it’s important he settles and doesn’t get stressed - so it’s best to just set it up like his current plaza - there will be less room in the middle but as long as everything fits, being a bit cluttered is ok. Main thing to check is access - ie is there enough space for him to get into a tunnel at both ends.
When I moved Tino from the 120 to the 100 the layout was identical - I just lost one large item which he never used as there wasn’t discernible for it. However I did realise later that it was a bit of a squeeze to get into his tunnel! But I’ve adjusted that now.
Final tip is - once you have the new cage all set up - hide lots of treats and add plenty of food and move his entire nest and board and house contents across with his house. Lots of treats will distract him from the change - finding them.
Final tip 2 is once the new cage is all set up and before you put him in, is to clean out his old cage completely and clean around the area of his old cage and put it away somewhere - out of the room. They have such a strong sense of scent and if he can smell any remnants of his old home in the room it could drive him a bit crazy and he would be stressed and not settle.
Even if his house contents are a bit messy or smelly - just move it all anyway and even a little bit of peed on substrate in the same place.
Then no cleaning or spot cleaning for two weeks. He needs that two weeks to make it his own. It’ll be fine for two weeks even if it starts to get a bit whiffy
If he has a separate pee area then after one week you could maybe spot clean the pee but not too thoroughly - a little bit left is ok.
Technically old age starts when they're about 18 months, but I think of it is nearer aged 2 as that's when it becomes noticeable. Between now and 2 though, keep an eye on how he manages with his back legs. They can start to struggle with them. I first notice it when they can't quite climb into a sputnik. It's usually about 2 when I first notice some hair loss or thinning though, but I suppose it can vary and it might be more noticeable with a very dark coloured hamster.
She located me because she has cold hands and could feel a warm spot in the vast amount of bedding in my cage 
I think they are at the peak of confidence once they get to a year old and more tolerant with us by 18 months.
She is usually quite frugal, but she wants me to have this and we are hoping it will be a good move for both of us. I am looking forward to getting my paws on the wheel 
and 
Whrb you say 2024 version - is there a new 2025 version then? I wasn’t aware of a new. Version 
