Ordering fields within mini registration form

Hi,

I would like to know how to ordering field within the mini registration form.

According to the current form (see screenshot), I would like to present these fileds as following :
- First Name and Last Name (step 1 of full registration)
- Password (step 1 of full registration)
- Email (step 1 of full registration)
- Select your index (step 3 of full registration)
- Select your hand (step 3 of full registration)
- Terms (step 1 of full registration)

Shall I put the custom fields in the 1st step? I'm not sure it impacts the order.
Shall I use a particular name as Unique Key (e.g. field01, field02, field03...) to order them?

In addition, I noticed that the placeholder styles for select your index and select your hand are diffrerent from the other fields like for instance Email. How to align them on this style?

Regards,