Apple ID problems: no password, no phone number, or anything

Hello!

I have an issue for a long time with my previous Iphone 5S.

The thing is that Apple ID for this phone was created for me by Sellers, so i never had an opportunity to check for the passwords and how it was made.

I changed phones a lot of times and this phone was with my mom since that time.

I don't remember if I tried to sign in or sign out, bur for some reason it started to ask for passwords all the time: to go to settings, to go to app store or to do anything, it requires password for Apple ID that i have no connection with, neither does my mom, because she just can't use such stuff.

Now in order for her to go to any app, the device keeps asking and i have no idea, how to reset the password. Whenever I go to "forgot your passwrod", the Iforgot asks for phone number that was authorized with this phone and i don't have that old phone number or email address to change it. I can't sign out to create new Apple ID, cause in order to sign out, I need to sign in.

Please help me. Phone works completely fine, but it can't be used due to password issues.

Is there a way to reset the password if I don't have any info on the previous Apple ID? or Is there a way to sign out, so it won't ask for password? Because even if I want to reset the Phone itself, i need the password...