Q: какая третья по популярности письменность для токи поны?
Toki Pona has been using Latin characters since 2001, and sitelen pona since 2014. But there is another writing system — sitelen sitelen, also known as sitelen suwi. It was created in 2009 by Jonathan Gabel. This is what it looks like:

Most Toki Pona speakers today cannot read sitelen sitelen, and very few use it. While sitelen pona is genuinely used in casual conversation, sitelen sitelen usually only shows up for decorative purposes.
If you want to learn to read and write sitelen sitelen, you can use Jonathan Gabel’s lessons.