How do I open Android apps on my iPhone?

The only way to make an Android app run on an iPhone would be to get the iPhone to run Android first, which is not possible at present and would never be sanctioned by Apple. What you can do is jailbreak your iPhone and install iDroid, an Android-like OS made for iPhones.

Can you convert Android app to iOS?

Despite being different operating systems with different application frameworks and regulations, it is possible to convert an Android app to iOS. However, the process required a level of experience and expertise that not all developers have.