Sorry, but you made the mistake of trying to compare Hinduism to Christianity.
Christianity is a defined religion with boundaries of what is and isn’t Christianity.
Hinduism is not a religion in that definition - it is a collection of religions.
“Krishna” and “Ganesha” were not even worshipped before the 1st century.
Pre-Buddhism, the “Hinduism” in India was Vedic religion with a God of Thunder - Indra (who is analogous to othOdin etc,.) was the chief of gods with two “families” of gods: Ahuras and Devas.
This is analogous to the more primitve Nordic religion with the Aesir and Vanir.
The Indo-Irani branch of Indo-Europeans had a falling out with the Iranis raising the Ahuras to a higher level (and ultimately Zoroaster took one ahura - Ahura Mazda) as the only God of light (countered by Aingra Mainyu, the god of the Lie) and hte Devas became fireplace/hearth deities.
In India the opposite happened - the Devas were raised up and the Asuras were reduced to demon status (only becoming demons after influence from Christianity — Christianity came to india as early as 52 AD).
Anyway - Krishna is an “avatar” of Vishnu - who has, I think - 10 avatars, another of whom is Rama.
This “Vishnu” along with Shiva and Brahma are called “the Hindu trinity” - and this concept arose only in the 1st century AD — again, under the influence of Christianity.
Ganesha first is mentioned in the 2nd century BC as an Asura , but later in the 3rd century AD he becomes a son of Shiva.
To your question “My question is whether the Hindu belief in God is genuine since their various prayers to apparent deities that are substitutes. “ — i find that for many it is genuine. The more philosophical forms of hinduism have an “Atman” or a greater than all God, but one who is so ineffable that he doesn’t bother with and can’t be understood by the world.
Thank you for all the information in your two posts.