Answer 1

Black White Yes and no.
There are apps yes. Just search for mobile code editor
But you can only do so much with a mobile editor and compiler. Even as smart phones become more powerful they are still slow at computing in comparison to desktop computers.

Larger Screen size and input devices such as keyboard and mouse are more preferable for coding. Although you can run a smart phone in desktop mode it still isn't close to a native desktop experience.

Another huge factor is compatibility and support for the smart phone operating system. There are many mobile desktop counterparts but the desktop version has more features usually due to the mobile display and compute constraints.

So still desktop computing is more preferable when it comes to development.

Answer 2

SwiftUI, Pythonista 3, plenty of apps just have to look