R44 is an older standard dating from the 80s although the most up to date version of it was 2008 IIRC. R129 is a newer standard which was rolled out in three phases between 2013-2018.
There are no car seats which meet both R129 and R44 standards - you might be thinking of the quasi "dual-approval" which some infant carriers had if they were released roughly between 2015-2017, because R129 rolled out in three phases and for the first phase, only isofix seats could be approved, while belt fitted seats could only be approved under R44.
That posed a problem for infant carriers which are only isofix fitted when combined with a base. A lot of parents like the functionality to be able to seatbelt fit as well so there was a loophole allowed where the manufacturers could certify a seat + base combo under R129, but separately approve the car seat itself without base through R44. That loophole was not allowed for other kinds of seats, even if they had two different fixing methods, and it was closed once belt fitted seats came under R129 approvals as well.
The Joie 360 Spin is an older seat which is approved under R44. Joie i-Spin is an updated version of the same seat which uses the same seat shell and mechanism but allows an extra recline position and there are some differences with the inserts and they added side impact pop out wings and changed the headrest so that it would meet the side impact protection guideline of the R129 regulation. The original Joie 360 Spin doesn't have great side impact protection.
The fit list on the Joie seat is done by Joie, so it doesn't matter about the age of the car. It's also just a guide and you can contact Joie customer service and ask them why it's not approved if you like. They may give you some information as to why they have given it that rating.
In cars which predate the R129 regulation, you might only find reference to R44 child seats (e.g. Group sizes) but it's perfectly fine to use R129 car seats in older cars, they are designed to be backwards compatible as the seatbelt and isofix standards had not changed. The car manufacturer usually sets out general guidelines allowing or prohibiting various kinds of child seat in their manual, but it shouldn't prohibit you from using an R129 seat even if they are not mentioned. As the car version changed in 2012 I believe, it might be that the manual does reference R129 because it was in discussion by then, but equally it might not mention it at all.
In terms of safety, if the seat gets a good fit (all isofix indicators show green, no issues contraindicated by car seat manual) and there is nothing in the car manual prohibiting use of something about that seat e.g. some cars have a minimum distance between the back of the front seat and a rear facing child seat, then there are no safety problems. The vast majority of older isofix seating positions will accept an i-size seat, and even modern cars without i-size designated seats can use an i-size seat if they have isofix. Being able to certify a car seating position as i-size is to do with a certain invisible box worth of space within the cabin, which I understand this car does not have. But some i-size seats will be smaller than that invisible box.
The Graco Turn2Me is the same seat again, it's a direct clone of Joie Spin 360 and so it is the same size.
The Seat Mii and VW Up! are the same base model of car as the Skoda Citigo. Technically, they are identical and child seat requirements will also be identical. So it sounds like two posters have managed to fit the Joie 360 Spin if not the i-Spin itself in this model of car, plus the Honest John guide suggests it fits. As said, the i-Spin is very slightly longer front to back if it's used in the 6th recline position, because the Joie Spin 360 does not have that 6th position. But if your child is 1 year old, they don't need the 6th recline position, so it should not be a problem.