Can't delete account
Don't delete your account just to get rid of the data on a Yandex service. You can delete unwanted photos, clear your spam folder, or change the answer to a security question that you have forgotten through the service that stores this data. You can find a solution to your problem in the help section of the corresponding service. They are all listed on the main Help page.
Go to Delete Account on the page containing your personal info to completely delete your account. You will need to confirm the deletion by answering a security question, where you provided one. If you forgot this answer, follow the instructions on the I forgot the answer to the security question page.