I have Tableau Online. I have a few dashboards that I want to share without password access and embed in my public website. When I embed it ask for the password. I have tried various tableau authentication but its only available in Tableau Server.
What you are attempting to do is not possible. Guest access, which is what you are describing, is only available with Tableau Server. Tableau Online has a different licensing model and does not include guest access. An alternative you might consider is to publish your data to Tableau Public. Tableau Public requires no authentication.
This limitation is documented in the Tableau help files as well as a number of Tableau community forum posts on their website.