Help Please... Hard Resetting iPhone 4

[Marzipanogram]

I have an old iPhone 4 that hasn't been used for years.
But I've forgotten the unlock passcode.
I don't have iTunes installed or know my account details either.

How many guesses do I have before the phone is permanently locked?
Also, I've contacted Apple and they recommend taking the phone to a store to have it unlocked.
Will I be charged for the unlocking/wiping of the phone? (I asked them, but they wasn't sure).
I plan to get rid of the phone after it's been unlocked, so I'd need to know if it's cost effective or not.

Thank you.

 

[Big Elf]

Given that that particular model led to the 'you're holding it wrong' aka 'The Death Grip' comments and only works properly with a bumper case (unless you can hold it right) I doubt it's worth more than £15-20.

EDIT: Just checked. I paid £30 for mine 2 years ago and had to put a new battery in it.