I wonder where can I find valuable information about iOS user interface guidelines. I can't find any information similar to the Android guidelines.
Unless I'm misunderstanding your question, there are easily accessible guidelines for both:
In case the links ever fail. Doing a search for iOS (or macOS, and so on) Human Interface Guidelines will typically get you there as well. This is how many of us would get to them before the sites (I think they were only available in PDF, and random tidbits throughout the documentation sites.)