If your iPhone is your main and only device, I do advise NOT to install beta releases. Yes, it can be instable, by nature of a beta.
Wait for a full release, and even don't rush to install. You can live a few months with previous release and wait for 26.2 or 26.3.
For your app development, test on simulator, that's no risk.
You will find plenty of information from Apple, on the web, on what's new in iOS 26.
Topic:
Developer Tools & Services
SubTopic:
Apple Developer Program
Tags: