Jasem, I have an update about my issues.

1. Somehow I decided to try previous version, downloaded apk from apkpure and 2.5.1 connects and works! It can see stellarmate, it can connect, it starts ekos and devices. So I conclude that the issue is in 2.5.2. I had only one issue with 2.5.1 when it didn't connect, but anyway it is not 3 days of struggling. I will continue testing it.
2. Yes, I did that. As I said, webmanager and VNC were accessible from the same smartphone, while the app didn't see it, same as manual IP address didn't help.
3. I can