1) This function is only accessible by the user with Administrator role.
There is a function in the Opening Balance to stop any users from entering any transaction prior to the Opening Balance setup. This has to be done in order to manage the account balance.
The date at the Lock Balance sentence is set at the Financial Year End.
To unlock this, user can simply just uncheck the checkbox and click button Save. Then user can start create any transaction prior to the date mention in Lock Balance.