Buddhahood is a state free of all obstructions to knowledge and disturbing emotions. It is the state in which the mind is fully evolved.
Reincarnation is not an exclusively Hindu or Buddhist concept, but it is part of the history of human origin. It is proof of the mindstream's capacity to retain knowledge of physical and mental activities. It is related to the theory of interdependent origination and to the law of cause and effect.
Study and practice are both very important, but they must go hand in hand. Faith without knowledge is not sufficient. Faith needs to be supported by reason. However intellectual understanding that is not applied in practice is also of little use. Whatever we learn from study we need to apply sincerely in our daily lives.