If you want to learn about persistentAttributes, then you can read about them in the ASK SDK documents (https://ask-sdk-for-nodejs.readthedocs.io/en/latest/Managing-Attributes.html).
For a full list of the supported SMML tags in Alexa, go to the Alexa SSML reference page (https://developer.amazon.com/docs/custom-skills/speech-synthesis-markup-language-ssml-reference.html).
If you want to hear how different SSML tags change the way that text is spoken, check out the Google SSML reference page (https://developers.google.com/actions/reference/ssml). It has working examples of lots of SSMLs, but you can't edit them.
