Jesus went to the cross to show humanity it must die to its egotistical, self-centered and materialistic desires in order to allow the spirituality within us to manifest. Jesus' purpose was not limited to teach us how to reach heaven, but also how to create heaven on earth. The reason why there are so many religions is because each of us is at a different level of soul development and understanding. The various religions are necessary because there are people who need what these religions teach. Religion is a stepping-stone to further knowledge.
Religions are cultural institutions only.
Love is universal because love is God. Light is knowledge of higher spiritual realities and darkness is ignorance of higher spiritual realities. Our ignorance causes us to make mistakes from which we must learn. In the end, those who make the most mistakes will learn the most. God does not care about a person's religious affiliation, only his or her heart.