Account name auto fill

Hello,
Thank you for your response
I think I have over complicated the question.
Taking it at one step at a time.
First with customer name (Account_Name) from either case view or account view.
this has a autofill dropdown when I start typing.
Can I also have this for another field? (acc no. > Sage_code_c)

Next I would like several fields in the case edit view to populate on the account name I select.
I have tried to follow this article Auto Populate related fields - SuiteCRM Forum - English Language / SuiteCRM General Discussion - SuiteCRM
All the fields are from the account module (like the number of users and the expiry date.
what I have is

1 => 
		  array (
            'name' => 'account_name',
			'studio' => 'visible',
			 'displayParams' => array (
                'field_to_name_array'=> array(
                    'name' => 'account_name',
                    'id' => 'LBL_CUSTOMERNAME',
					'LBL_SAGE_CODE' => 'sage_code_c',
					'LBL_CONTRACT_END' => 'contract_end_c',
												),
										),
			'label' => 'Customer Name',						
			),	

but not working
the above link states
‘<field1_of_Contacts_module>’ => ‘<field1_of_Opportunities_module>’,
Sorry for my ignorance but what is “field1_of_Contacts_module”, How do I find this? is it via studio and take the field name or display label or the system label?

Many thanks