This operation cannot be undone. It deletes not just your account, but also all images videos and other data that was uploaded. You also need to delete the application(s) from your mobile device(s) - they won't be able to synchronize data with our server.
You cannot. The reason for this is that you can have several mobile devices connected to your account, and some of these devices could have been stolen. For ease of use, these personal devices don't ask for password for data synchronization. We don't have a way to check if the person who is using the device is the same one that has created the account. The online account is the authoritative. All account operations (including device removals) are handled through our website.
If you have used your Google account for registration, then you can also sign in with the same Google account. If you have used secret password authentication, then you can use the "forgot your password" feature (look for this link on the sign in page.)
There is no easy way to help you in this case. We have no way to tell if you are the original owner of the Google account, or you just want to get access to an existing member's account. You can, however cease using our applications through this account, and wait three months. After three months if inactivity, you can request us to delete your account. You can do this even if you are writing from a different email address. Then we send out a warning message to the email address that is associated with the account. If we don't get any response in due time, then we will delete the account automatically.