iCloud problems
I cant long into my gmail account but I remember my iCloud account and the security question.
iPhone 6
If Apple ID is set say example1@gmail.com , knowing Apple ID and password is not sufficient , you need correct answers for three security questions .
It's not sure you are already signed with Apple ID in iPhone , if you can't sign in with appleid.apple.com convert the account into 2FA Manage two-factor authentication from iPhone - Apple Support
Get a verification code and sign in with two-factor authentication - Apple Support
If password for gmail account is forgotten , reset the password using a web browser https://support.google.com/mail/answer/41078?hl=en&co=GENIE.Platform%3DDesktop&oco=0