how to get the android phone model, version, sdk details?

First of all, have a look at these "Build" class at android-sdk page: http://developer.android.com/reference/android/os/Build.html.

// Device model
String PhoneModel = android.os.Build.MODEL;

// Android version
String AndroidVersion = android.os.Build.VERSION.RELEASE;

You can use Build.MODEL and Build.VERSION

 String s = "Debug-info:";
 s += "\n OS Version: " + System.getProperty("os.version") + "(" + android.os.Build.VERSION.INCREMENTAL + ")";
 s += "\n OS API Level: " + android.os.Build.VERSION.RELEASE + "(" + android.os.Build.VERSION.SDK_INT + ")";
 s += "\n Device: " + android.os.Build.DEVICE;
 s += "\n Model (and Product): " + android.os.Build.MODEL + " (" + android.os.Build.PRODUCT + ")";

Example output:

 OS Version: 4.9.106-perf+(1909112330)
 OS API Level: 9(28)
 Device: OnePlus6
 Model (and Product): ONEPLUS A6000 (OnePlus6)