Signing in here proves the account is yours. Your Google email is used once, to send the confirmation, and is not kept.
Your store, lists and pictures live only on your phone. Uninstalling Sanchi clears them. If the law needs any record kept, the privacy policy names it and for how long.
This cannot be undone.
Your account is deleted.
In Gmail, delete the Sanchi filter and remove your Sanchi forwarding address. Anything sent to the old address is dropped.
A confirmation is on its way to your Google email.