Odoo customization

I am using Odoo / OpenERP for my web shop and need these crucial changes: 1. Every time a user adds something to their cart, it redirects to their cart. I want to stop this. 2. I want to have a Quick add to cart button that is simple to use: Shows a + and - button to increase/decrease quantity and the add to cart button. 3. Force user to register/login before checkout 4. Save user's shopping cart so they can reorder their cart. Kindly quote for these four changes. So that I know you have understood my requirements, kindly suggest how these can be achieved. Any proposal that is simply a copy and paste will be IGNORED!