No, it’s not a LTS, 4.0 will be the next LTS version.
For new features, look at the combined list of 3.1 and 3.2 features:
Minimum kernel version is supposed to be 2.6.32 but we don’t very actively test on such old kernels and obviously a lot of features would be missing on such an old kernel.
3.12 or higher is in general recommended as that’s when the user namespace first got introduced.