If you want to apply conditional validation on 'Middle Name' or 'Last name', then you need to add 'First Name' input as 'Bharat'
{{userFormGroup.controls.firstName.errors.maxLength.message}}
To apply validation here, write 'Bharat' in 'First Name' textbox because it is conditional expression. and maximum length is 16
Conditional Expression with type 'function'
{{userFormGroup.controls.middleName.errors.maxLength.message}}
To apply the validation of lowerCase on 'Last Name' field, write 'Bharat' in 'First Name' textbox because it is conditional expression. and maximum length is 16
Conditional Expression with type 'string'
{{userFormGroup.controls.lastName.errors.maxLength.message}}
{{userFormGroup.controls.userName.errors.maxLength.message}}