urgr8 said:
1) Anybody can fill the forms on behalf of sponsor and application ?
They can be helped with filling out the forms, but, unless they use a representative, all the addresses and signatures have to be theirs. Also, there will be personal questions in the forms and they will have to know the answers and additional details in case of an interview at the embassy. They will definitely will be asked about informations in the forms at the landing interview.
Is there a reason why the sponsor and the principal applicant can't fill out the forms for themselves?