Huh? You're allowed ANY manual transmission cars as long as it meets the other rules, you need to have done your P's test on a MT car and it must meet other P plate power restriction regulations. Green P plates have no restrictions regardless of whether you took your P's test on AT or MT but still have the power restriction.
Yeah, no limit on the amount of forward gears. Most new-ish small cars come with six-speeds in the MT even in the base model, like the BL and BM Mazda3.