False. Some sins are worse than others. You've been hanging around low-tier Christians if the majority of them think that way.
Sexual sin is grave matter.
Discussion
Only if you are Catholic.
Puritans? They were a sexy group.
https://www.bostonmagazine.com/arts-entertainment/2016/10/18/puritans-and-sex-myth/
What you really mean is "only if your religion predates Calvin and Luther," which is true.
You realize the once-saved-always-saved and all-sin-is-equal theology is less than 500 years old and still an extreme minority opinion, right? They are not teachings of Jesus.