Masah of the head

Q: When making wudhu, how should the fingers be positioned during masah of the head? I have heard some ulama saying masah of head should be made with all 5 fingers with an open hand, or some say masah of head should be made with 3 fingers (middle ring and baby fingers). Please advise.

Keeping two names

Q:

1) When 2 names are kept, eg Faathimah Zahraa, then is it fine -or not advisable- to call by only one of the names at times. Eg calling the child sometimes by both names, sometimes only faathimah, sometimes zahraa, is this fine?

2) When calling by both names together, would it be pronounced Faathima-tuz-zahraa', or Faathimah zahraa', or would both be fine to say?