Yes, the Iranian Revolutionary Guard is a terrorist organization is a terrorist organization, because they wish to effect change by terrorizing others. The name of the Iranian Revolutionary Guard is telling enough as to the truth goal of the organization. They want to have a revolution, and they are not afraid to resort to terrorist actions to make it happen.
Yes, they should be considered a terrorist organization, because they have an extremely large army. The organization's mission is to protect Islam at all costs, and that includes taking whatever actions are necessary. The Iranian Revolutionary Guard is not afraid to use force and terror to make their point and convert others to Islam.