Code for sorting by default for ascending order or descending order in Magento 1
Go to your themse’s local.xml and place the code
Override system.xml in Magento 1
Overriding A System.xml file for adding addition settings to an exist module in a new module. Module name is (Namespace_Modulename) Note : Change as per requirement like change groupname,sectionname,fieldname.
Code for adding extra fields at customer registration in Magento 1
Then after for saving these datas into database.Go to register.phtml (Path can be :- app/design/frontend/default/bootstrap/template/opc/customer/form/register.phtml
Code for adding addtocart button and quantity box at the category list page in Magento 1
Open list.phtml and any other related on which you want to display the addtocart button and quantity box.
Code for making the comment field required on checkout page in magento 1
Note : put this code in skin/frontend/default/your_theme/js/ your_theme /opc/checkout.js