Hinduism: eternal Sanatan Dharma
Hinduism: can be best defined as Sanatana Dharma... something which exists from times immemorial. Hinduism does not have a beginning... it exists ever since Humanity came into existence. The bane of Hinduism is Dharma... which also forms the base of all Religions existing on Mother Earth. No Religion can ever survive without a Dharma. Dharma is the root of all Religions. Why?
Talking of Jainism we cannot understand the basics without delving into the Life of the 24th Tirthankara Bhagwan Mahavira. It was only in the time of the 24th Tirthankara Bhagwan Mahavira that Jainism rightly came into existence. Whatever form of Jainism existed before the 24th Tirthankara was limited to the Spiritual Masters only. All that was knowable to these Spiritual Masters was not available to the masses for the prime reason that the intellect of a common man was not as developed as was required to fathom the depths of the Sacred Wisdom we know as jaina doctrines.
During the times of Bhagwan Mahavira... the common masses came to understand what was being taught by the masters of the era. Gradually as the momentum picked up... the followers of Jaina doctrine came to be known as Jains and the following Jainism. Before Bhagwan Mahavira the existence of Jainism as such did not hold good as it was only limited to the Spiritual Masters of the day.