Small Shopify Task

Hello Freelancers, We have a shopify website [login to view URL] What we will need: 1. Product variants with radio buttons (when variants are sizes) 2. TOP-sellers section for the front page 3. free gifts functionality a. three levels (buy for 100 get gift A, buy for 200 get gift B etc) b. visible in shopping cart etc. Require good knowledge of Liquid (especially number 3) While you apply The following notes are mandatory: 1. Live shopify work links and what you have done with those websites 2. Need elaborated description how will you solve the above points. No other bla bla bla... 3. The money will be in milestone phase. We only release if we are 100% satisfied. You can not pressurize us to release payment or partial amount without satisfying us. 4. The site is live so I want to know how you complete the task without loosing any of my content, design or I don't want to make my site under construction. 5. Time of support period.