No, it's not mandatory for your iPhone app to run on iPad unless you specifically want to make it compatible. You can certainly build an app exclusively for iPhone. Check out this guide on creating an iPhone app for some helpful tips: https://www.cleveroad.com/blog/how-to-create-an-app-for-iphone/.

Hi! According to the blog of a software development company (https://www.cleveroad.com/blog/how-to-create-an-app-for-iphone/), you cannot use Windows 10 to develop iOS apps natively. Apple's development tools, including Xcode, can only run on macOS. However, there are workarounds to develop iOS apps on Windows 10, such as virtual machines or remote Mac servers. These options may be less convenient and require additional resources, but they allow developers to work on iOS projects using a Windows 10 computer. It's important to note that developing for iOS requires a developer account with Apple and knowledge of Swift or Objective-C programming languages. The resource linked above provides a detailed guide on creating an app for iPhone, including the necessary steps for developing on macOS or using workarounds on Windows 10.