The iPhone models currently sold on apple.com work with nano-SIM cards and eSIM voice and data plans from compatible carriers or providers.* And they work on many 4G LTE networks around the world. Contact service providers for details.
Available space is less and varies due to many factors. A standard configuration uses approximately 10GB to 12GB of space (including iOS and preinstalled apps) depending on the model and settings. Preinstalled apps use about 4GB, and you can delete these apps and restore them.
** Trade-in values will vary based on the condition, year, and configuration of your trade-in device. You must be at least 20 years old to be eligible to trade in for credit or for an Apple Store Gift Card. Not all devices are eligible for credit. More details are available from Apple’s iPhone, iPad, and Apple Watch trade-in partner for trade-in and recycling of eligible devices. Restrictions and limitations may apply. Payments are based on the received device matching the description you provided when your estimate was made. Apple reserves the right to refuse or limit the quantity of any device for any reason.