#3366

#1. Rename “Billing Details” to Customer Details on the checkout page: I rename for you.
#2. Variable product: With your idea, you need to create unit price, ex: 100$/1kg, then create variation product with options ( ex: 0.5kg, 1kg, 0.25kg). Price on variation will be calculated and auto-update for variation. When update, you only update unit price.