Apple will have limited iPhone Duo units available in stores on Friday

Apple on Wednesday said it will have ‘limited’ numbers of its folding iPhone Duo phone available for walk-in customers when the device launches on Friday, after initial online orders sold out in minutes and pushed delivery times for some customers to January. Apple announced its first folding phone in September, with analysts expecting it to quickly come to dominate a niche segment where rivals such as Samsung Electronics and Huawei Technologies have sold premium offerings for years. But the iPhone Duo is also a more complex product than standard candy-bar iPhones, with a tight-fitting hinge…