Hiya!
You are very welcome! Sorry I can't remember it all exactly, it was about a month ago I filled in the form.
The 185 day thing I don't really know...
If I'm remembering right, you've moved to the UK within the last few months, right? If you have, than you can actually drive on your US license for 1 full year. That year starts on the day that they stamped your visa for entry at the Airport. Which is great, cause you can get all sorts of practice in on that. You don't even need to have an "adult" in the car with you. haha.
You do need to have your provisional license to take any of the driving tests. So it's a good thing for you to have so you won't worry when you are ready to take the tests.
What a lot of people on here suggest doing is to take some driving lessons specifically to learn how to pass the UK driving test. You already know how to drive just not all the niceties of driving in the UK. It's what I'll be doing, but I waited too long and now I have to have an adult with a license with me and the red "L" on my car... YAY! I'm so excited!
Make sure she also writes what's needed on the back of the photo, again without that you won't get your license. That's where she proves it's a photo of you. My husband had his boss, our mutual friend, do mine for me.
Then passport it is for you! I had the BRP card cause I'm on FLR(M).