Ca final re registration

Hi All, One of my friends artcleship. completed and he has been working in a company since 3 years. He is planning to write exams in 2016 May. Now he wants to re register , following are the doubts 1.Is the new registration applicable from the date of re registration or from the date of expiry of original registration? 2.Any CA signature is enough or need to be signed by the CA under whom the articles have been completed.