Its difficult because in the UK, we don't have a simple levels system like you've got in the US. You'll also find that in the UK, they are a lot more restrictive about what they can do at the younger age, due to concerns about burn out etc. Here in the UK, they don't believe in pushing children too young, and a lot of places don't children to compete (or rather, be ranked) until the year they turn 8... so it is quite different.
To complicate things further, the skills vary according to the level the child is competing at. My DDs are 8 and 5, and they compete...
Most children who do recreational gymnastics are able to badges (like BAGA) these go from 10 to 1 and then Bronze, Silver, Gold. However lots of clubs (my DD's club included) don't like them and so do their own thing.
We're in South West England and my DD1 (8) is just about to take her County Grade 2 and her Regional Grade 13. She is following the in age route. Next year, she will take her national grades (when she is old enough) but she will not take her compulsory grades (which are the very hardest). So a child who is taking her regional grades will do harder tricks at an earlier age to a child who only competes at county grades and so on...
My DD at 8 (and going for country, regional and national grades but not compulsory) can do most of what you describe. She can do backflicks but not back flips on floor and is currently just learning to do sommersaults. Some children her age can already do them.
On the beam she can do backward walkovers, but not tick tocks, forward walkovers, handstands, cartwheels and roundoffs off a beam.
On the bars, she can upstarts, straddle on undershoots, squat on to catch (and swing from) top bar, cast to back hip circles.
DD2 (5) is in a development squad, one day she will compete and according to her coach, at a similar level to DD1.
She can do cartwheels and roundoffs on the floor, but they have not been taught them yet. In gym class they're still learning to cartwheel over a piece of soft play equipment.
In terms of the beam, they're only taught to tip toe walk along the high beam, bend down, touch the sides, do an arabesque and then a star jump off the front. She will do this at her first grades competition next year, but with a half backward roll added in.
On bars, she is learning to do three chin ups in under grip, swing round, do three leg lifts, and then three chin ups in over grip. She will also need to swing and regrasp. This will be what she will need to do at her first competition next year.
In the UK, the level they compete at depends on the year of their birth, so although my DD is 8, she competes at the 9 year group this year, as she turns 9 this year.
Assuming your DD turned 10 this year, then she would be one year ahead of my DD and so at my DDs club would be doing
Wiltshire county grade 1,
South West Regional grade 12
National Grade 8.
If your DD2 turns 7 this year, then she would be able to take her county grade 4.
You can look up what skills this means by looking it up on youtube.
Also, the gym club 'tnag' have put together a guide to british gymnastics - so that's worth a look. just google 'tnag'.
Finally, I say all of this, but what I write might be entirely inaccurate - British gymnastics are known to change their minds on the rules!!
But I would expect that your youngest in particular to be ahead of a lot of Briish girls as when they're younger the focus is very much on the basics. Your eldest dd, being a year ahead of my DD sounds probably in line with most british gymnasts, but I suspect maybe a little behind some of the elite girls. Having just come from a competition with some elite gymnasts there, those girls were doing what you describe of your DD at 8/9.
Hope this ramble helps...