"Sticky" features remember the last setting you used, and continue to use that setting unless you change it.
Asks: When replying to questions, you can reply privately instead of posting the answer to your blog. Future replies will stay private until you update your preferences and switch to public, and vice versa.
Posting: Once you post to a blog, all future posts will post to that blog until you switch when selecting a post type. To switch, tap on the blog's name to show a list of the other blogs on your account. Then tap on the blog name where you'd like the post to publish. So yeah, be sure to select the right blog before pressing “Post."