How to find potential users for apps uploaded to the app store? How to promote, who can provide guidance, thank you!

I filled in some information when publishing the application and felt that the icon was not good enough. I made another one and used this new icon in XCode. After running it on iPhone, the icon changed, but there was no change in the submission section. Now the application is in the "ready to submit" stage and I don't know how to change it to the new icon. Can anyone give me some guidance? Thank you!

I have developed an application using Kotlin and Swift languages, which has been installed and run on an iPhone. It can also be installed on an iPad. Do I need to go through a testing process to publish it on the app store? Also, as a developer from China, are there convenient payment channels for developers?

I want to use Swift language to write code for drawing multiple polygons. I would like to find some examples as references. Can anyone provide example code or tell me where I can see such examples? Thank you!

I use Kotlin Multiplayer Development to develop iOS applications. I access the methods in the Kotlin class of the shared module in the ContentView.swift file. Functions without parameters can be used normally, but functions with parameters cannot. For example, the 78th line of code on the left side of the screenshot works, but the 79th line does not. Can someone please tell me the reason? Thank you!

I created a project using Kotlin Multiplayer Wizard in Android Studio, but some of the AndroidManifest.xml files are red and cannot be used. Can someone please tell me the reason? Thank you.

I have written an Android application in Kotlin language in Android Studio, which can run on mobile phones or tablets. Is there any quick and easy way to package it as an iOS application? Show screenshots of two Android applications running