"The Proving" is fast approaching! Get to Hunter Rank 11 by February 28 and face a giant Anjanath to get the Horizon Zero Dawn hunter gear. (PS4 exclusive) pic.twitter.com/LGP0IgXRz0— Monster Hunter (@monsterhunter) February 12, 2018
This event will run until March 5th apparently, so not a whole lot of time if true. Some people will have missed out on the Palico armour that turns them into a Watcher, so if you want to get this set, you should make sure you get to HR11 by the end of the month. At least they're giving everyone plenty of time to get there - HR11 doesn't really take that long, you just follow the story missions and you'll get it.
The armour set will be a full armour set and will turn your avatar into Aloy - regardless of your gender or skin colour or anything else. You have to wear it all or none of it - same with the Palico armour. With the Palico you can give it a different weapon though, so the same should be true here.