Premise:
"The south remained dominated by the Hindu kingdom of Vijayanagar for the next 250 years."
Hypothesis: The Hindu kingdom of Vijayanagar dominated the south for 250 years.

yes

Premise:
"Once the parade is finished, an exhibition of the award-winning flowers and displays is put on in a lovely old house in Rua dos Castanheiros."
Hypothesis: The flowers most likely to win are the pink tulips.

it is not possible to tell

Premise:
"Suppose that Unsolved Mysteries called you with news of a long-lost identical twin."
Hypothesis: What if they wanted to let you know that you were indeed an only child?
no