Q: How can I access the checkout page JavaScript code? (index.js)
You are free to add your own JavaScript to the page, but you cannot edit the core JavaScript file.
Q: How do I sync my products?
In the builder you can find the Sync button on the Funnel tool bar as well as on the plugin when you click the gear icon.
Q: Input fields zoom in on mobile apple devices
Change the font size to 16.