You cannot change the system font on a non-jailbroken iPhone. However, you can use the font in specific apps (like Pages, Keynote, or Adobe Spark) by:
You may not redistribute or use SF fonts in commercial software, logos, or websites outside Apple’s ecosystem (e.g., Android apps, Windows software) without explicit permission. For web use, Apple provides a limited “SF Pro” webfont only through specific CDNs for Apple‑related content. ios-v14.ttf font download
of apps for Apple platforms. Using them on websites or in other commercial software is generally prohibited by their license. Security Risk : Downloading You cannot change the system font on a non-jailbroken iPhone
Now that you've installed the iOS-V14.ttf font, you can use it in your designs. Here are a few ways to use the font: of apps for Apple platforms
intended for use on Android or Windows to mimic the iOS look. Authentic iOS Fonts & Sources