I want to get the parent object field name in query string of child object

1)Product(CL__Product__c) is parent to Account object. on account object having product(Product__c) lookup.

you want to say that product is master of account and again account is parent to product.Can you clarify this point?

2)when i update account field, i want to display the Product(genesis__CL-Product__c)  from  on Account  Product(Product__c) field.

It means that when you are going to update account field with product__c field on same time you have to update Product(genesis__CL-Product__c).Can you clarify those points.