Only 1- the experiment can not show a cause and effect relationship if there are more than one factors contributing to the outcome.
Answer: Well, deforestation is cutting down trees, and many arboreal animals live in those trees. So if they have no proper shelter, they would have no place for personal activities such as breeding, feeding etc. And without those important activities that they have to do everyday, the population of arboreal animals will keep on decreasing until they go extinct. Though that's not the only problem. The herbivores won't get anything to eat, hence not letting the omnivores or carnivores get their food. As you can see, deforestation can create a huge environmental imbalance.
The statement is - True.
The Tasmanian tiger went extinct because of the extensive hunting by the new settlers. People were killing the Tasmanian tiger because they thought that it is the animal responsible for the killing of the livestock, but at the end it turned out that they made a huge mistake and that actually the feral dogs and the dingo were the ones responsible for that. The last Tasmanian tiger was a female and died in captivity under very bad conditions.
Even though people use the term Tasmanian tiger (because of the stripes) and Tasmanian wolf (because of the dog-like face), it is an animal that is not related with neither the cats nor the dogs, but instead it is a marsupial, the biggest marsupial carnivore in the recent history, and its real name is Thylacine.