Should scientists revive extinct animals?
Yes, especially man eating animals only on three conditions:
Yes, especially the extinct hominins, asking for a old friend.
Depends on the animal. Recently extinct animals where there is still habitat for them, sure. Especially if there would be ecological benefits to said habitat. The Tasmanian Tiger or Carolina Parakeet for example. Long extinct animals like the Woolly Mammoth, doesn't make sense to me to revive them when they'd essentially be confined to zoos.
That depends on the animal and how/when it became extinct. If its an animal that went extinct within the past few hundred years (tasmanian wolf or the dodo) and due to humans then I'd be in favor of reviving the species. If its something that has been extinct for thousand of years (smilodon or the mastodon) or longer and may no longer have a place in the current ecology then I'd say definitely not.