Cage suitability...

Personally I'd not use that for a hamster, it looks way too small. The bigger the better I always say (although obviously make sure it's escape proof haha)!

I personally prefer the big glass ones with plenty ventilation holes which are marketed for rabbits (and way too small for rabbits in my opinion). You can put different levels into it and can also create a decent area on the bottom floor for digging and foraging, however I'd personally probably add some sort of "background" to at least three sides of those ones (making sure not to cover ventilation holes) so that the hamster doesn't feel too exposed either.

I feel that cages marketed for a particular animal are usually in my opinion much too small for that type of animal, as sure it has some space but I feel it can get very boring and the bigger a cage is the better. Plus I'm not so keen on plastic cages or ones with bars.

Just my personal opinion, but I would always go for the biggest enclosure possible and really go for the behavioural enrichment in any way I could, plus changing areas of the environment now and then depending on the animal and how it would cope with that, so that the cage doesn't get too repetitive and boring.

Haha the German cages are absolutely not all that minimum size, at my old work there was some teensie ones, which I never had to sell as I was always quite happy to inform customers that they were way too small.

Nuh-uh! Gerbils need huge tanks that can be filled so they can dig, I think they need a minimum of 1metre long, and about 50cm high (they are talented jumpers). Nice require a different set up altogether, they are so tiny and fragile that they could easily hurt themselves in that sort of cage, but also escape from it pretty quickly!