Reading more and more mythological stories, I realize that the first religion on earth is Hinduism.(Source1)(Source2) List of top religions:
Hinduism Oldest of all (Also known as Sanatana Dharma)
Buddhism also derived from ancient Sanskrit follower Buddha which sanskrit is the primary sacred language of Hinduism.
Judaism came before Christianity.
Jainism also before Christianity (6th century B.C.)
Christianity came in to existence in Kaliyuga according to Hinduism which explains about Yugas and BCE.
Islam came after Christianity.
Answer to the question in title will be helpful to all those who have doubt about oldest religion.