In ancient times, lots of people believed in lots of different Gods, it was often a tribal thing. Judaism was one such religion, except, instead of saying that its tribal Gods were better than all the others, it started saying that there was only one God (rejecting the former worship of, for instance, Yahweh's wife Ashtaroth), and that all the other tribes around were worshiping fake Gods.
This didn't bother many people, except the Romans who had a religious policy of accepting the reality of all the Gods of subject peoples, provided that those people were willing to accept, or at least tolerate, the worship of a large and growing pantheon. Multiculturalism basically. The Hebrews were not willing to accept this, which led to considerable friction.
Monotheism is fundamentally intolerant. If you believe in one true God, and one true teaching revealed by divine inspiration, anyone who disagrees with you on any point of doctrine must therefore be worshiping a false God. For this reason, Adonai (meaning "Lord"), is apparently the same as Jehovah/Yahweh, but Baal (which also means "lord"), Jove and Adonis are considered false Gods by Jews and Christians.
This is problematic because the bible is plainly not a coherent document dictated by God, or if it was, lots of people who wrote it down must have been hard of hearing. For instance, different books of the old testament cannot even agree whether or not first born babies should be sacrificed.
Around 2000 years ago, a Jewish cult arose which began proselytizing, attempting to convert non Jewish people to the cult. This was Christianity. It picked up ideas from paganism, especially Greek paganism, and as it spread it adopted many local festivals and local Gods became saints. Christianity in different regions began to diverge into different religions. There was an early split between the Greek dominated Orthodox church and the Latin dominated Catholic church which coincided with the Roman Empire splitting in half. There were multiple gospels written years after the death of Jesus, all different, all claiming to tell the life story of Jesus.
The early church decided that 4 of these gospels were "divinely inspired" and the others weren't. Pretty sure this wasn't a happy consensus, but any religious groups which disagreed no longer exist. Matthew, Mark, Luke and John are quite contradictory and each puts a different slant on the story of Jesus.
Early bibles were handwritten and copied by semi literate people. The fragments which survive are full of transcription errors and inconsistencies. Some parts such as the ending of Mark's gospel have changed over the centuries. The story of the woman caught in adultery was originally just a footnote, later incorporated into the text.
For centuries bibles were only in Latin and Greek, but with the invention of the printing press, they were translated into many different languages. Even then there was an awareness that not all bibles were the same, and that translation errors were a possibility. There was also disagreement about which books to include, and some books (such as Tobit) are now commonly omitted from Protestant bibles but included in Catholic ones. Now you can choose from around 30 different English translations of the bible, all slightly different.
The translation and mass printing of the bible really caused the sh!t to hit the fan. A major rebellion against the established church began, and unlike previous ones, such as the Cathars/Bogomils, this one survived. Now lots of people could read the Bible and attempt to interpret it, and of course interpret it in entirely different ways, because most of them didn't actually read all of it, they just cherry picked bits of it to support their personal agenda (reading the whole of the bible is a great way to become an atheist. Most people who try stop around Leviticus). In many cases these different interpretations were political, an excuse to wage war on people in another region who interpreted the Bible differently. Methodism is not really any different from Anglican (protestant) Christianity, it was just a rival church to the church of England started by John Wesley who wanted to call out the Church of England for its apathy.
Some distinct new religions have budded off from Christianity, such as Mormonism whose founder claimed to have received a new book of the bible by divine revelation, Rastafarianism whose origins are obscure but regards the deceased Emperor of Ethiopia as a prophet, Voudoun and Santeria which fuse Roman Catholicism with pagan traditions from Africa and Latin America.
In answer to your first question, none of them are true except possibly, in some cases, in a poetic or allegorical sense. They are however, sometimes useful as a way to unite people, and they don't seem to go away easily. When one religion gets discredited, people find something new, and often more irrational to believe in. The rise of spiritualist churches happened very soon after the publication of "The origin of species". Communism tried and failed to eradicate religion. I have traveled and lived in formerly communist countries and a variety of religions still survive.
A quick tour of the weirder corners of the internet will reveal that despite education, science, modern medicine etc. plenty of people are clinging to superstitions from centuries ago, or inventing new ones. A lot of mainstream religious Christians etc. will dismiss these as cults, but actually the leaders of these cults are behaving a lot like Jesus, a man who told his followers to sever ties with their family and non-believers for instance, who used faith healing stunts and other conjuring to win over gullible converts (I have little doubt that the "cripple" he told to "take up thy bed and walk" was an able bodied stooge, as was his old friend Lazarus. Modern faith healers do very similar things).
Islam, another monotheistic religion has similar issues: Hadiths or sayings attributed to Mohammed, collected years after his death, disputes between rival groups claiming to have the "true interpretation" of the Koran etc.