More likely migraine. Auras can be caused by a number of different causes--though migranes are far more likely than a brain tumor. I would suggest you discuss this with your primary care physician.
Can be either. Migraine is much more common than a brain tumor. But one can get an aura with both. You can also have it with epilepsy without an underlying tumor.
Not Typically. Classic migraine symptoms are not generally associated with brain tumors. However, headache can certainly be a symptom of a brain tumor.
Maybe. The symptoms of a migraine can include a number of things like headaches, light sensitivity, nausea etc which can indeed by caused by a brain tumor. However, migraines are far more common--i would suggest you discuss this with your primary care physician.