Make the following modifications/improvements to a Shopify store:
1) Add an "add to wishlist" or "mark as favorite" button to each product that will enable customers to save products that they plan to purchase in the future.
2) Add a few Tamil font typefaces to the site, the fonts are available from [url removed, login to view]
3) For Account creation page, add a customizable error message when user tries to create an account without filling in mandatory field. The error message should indicate specifically which field has not been filled up yet.
4) Add ability to sort a collection / products that are marked as discounted or on sale so when you select the option to sort by offer items, the product with the most discount will appear first.
5) Add + and - button to increase/decrease product quantity in the my cart page.