Green Finger Limes are fairly similar to west indian lime, perhaps a little sweeter. Other colours are very different, ranging thru yellow types, lemon to grapefruit flavor, to berry flavors in the red types. They grow naturally in the subtropical rainforest, from the warmer coast to high up into the mountains, which is much colder.
I have found them to be true to their colour from seed, ie from wild fruit, but in a greenhouse they cross easily.
This would apply to plantations with many varieties of finger lime..
They will also cross with other Citrus flowering at the same time.
About 5 years from seed to fruiting, probably faster if you can grow it faster to height.
The winter day temp here is 12 to 14 'c on the coldest days. average is 17 'c .
The usual overnight minimum is 0'c but can get to -5 which causes severe frost damage.
Anything like 5'c to 10'c overnight is no problem, but they wont grow much.
Keeping them warmer would be better. (Yes could overwinter in room temp. around 20C).