You cannot delete your yahoo account from a mobile app. You have to use the delete link from a desktop browser.
Delete Yahoo - Website - Slides & Instructions
Please note, after deletion do not log back into your account. Logging back in will reactivate your deleted account.
Deleting Yahoo? Share Your Experiences
Questions & Answers
Yes. Deleting your Yahoo account will disable all other Yahoo associated services.
Facebook's single sign on service makes logging in and creating accounts for apps, games, and services easy. But when you connect to Facebook you give those apps access to your data — a lot of your data. So it is a good idea to log onto facebook after deleting Yahoo to remove facebooks third party access. Essentially this will break the link between your Facebook account and Yahoo. To do this, follow the steps on how to remove Facebooks third party access.
Yahoo says the deletion process takes about 90 days to complete. After this your information will be removed. If you want your data scrubbed from Yahoo's servers sooner than that, you'll want to go through and delete your Yahoo! emails, Flickr photos, and Yahoo! Contacts before completing the account termination process.
No. It’s incredibly hard to contact yahoo directly by phone or direct email. The steps above are the best method for deletion. Don’t ever count on ever speaking to anyone directly.
Yes, but there is a small window for this. If you sign onto your account within 40 days of closing it the account will be automatically reactivated.