Hello @highlightings !

1) If you mean how to add smth as the label which should be available in the forms - then there is no such method for now. If you mean how to save it via the form into some content info - then you may transfer the super global array like $_POST['labels'][]

2) In the given example the id of the post can be found in the bx_posts_posts table. If you have the deal with the profiles you may read about here:

https://unacms.com/wiki/accounts-profiles