Jamaat Salaah and Imaamat

Masbooq (latecomer) joining the Imaam before Salaam

Q: Whilst performing Salaah with Jamaat behind an Imaam, if a Masbooq (latecomer) joins the Salaah after the Imaam has completed four rakaats and joins just before the Salaam.

1. Is it necessary for him to recite the tashahhud with the Imaam for his Salaah to be valid or is it sufficient for his Salaah to be valid that he joins in the Salaah before the Imaam makes salaam?

2. Should the Masbooq recite only Tashahud in the Qa'dah or also Durood Ibraaheem and Duaa after Durood.