public String getAppVersion() throws PackageManager.NameNotFoundException {
    PackageManager manager = getApplicationContext().getPackageManager();
    PackageInfo info = manager.getPackageInfo(
                            getApplicationContext().getPackageName(), 
                            0);

    return info.versionName;
}

To get versionName and versionCode of current build of your application you should query Android's package manager.

try {
    // Reference to Android's package manager
    PackageManager packageManager = this.getPackageManager();

    // Getting package info of this application
    PackageInfo info = packageManager.getPackageInfo(this.getPackageName(), 0);

    // Version code
    info.versionCode

    // Version name
    info.versionName

} catch (NameNotFoundException e) {
    // Handle the exception
}

To get the time at which your app was installed or updated, you should query Android's package manager.

try {
    // Reference to Android's package manager
    PackageManager packageManager = this.getPackageManager();

    // Getting package info of this application
    PackageInfo info = packageManager.getPackageInfo(this.getPackageName(), 0);

    // Install time. Units are as per currentTimeMillis().
    info.firstInstallTime

    // Last update time. Units are as per currentTimeMillis().
    info.lastUpdateTime

} catch (NameNotFoundException e) {
    // Handle the exception
}

Here we can find some useful method using PackageManager,

Below method will help to get the app name using package name

private String getAppNameFromPackage(String packageName, Context context) {
    Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);
    mainIntent.addCategory(Intent.CATEGORY_LAUNCHER);
    List<ResolveInfo> pkgAppsList = context.getPackageManager()
            .queryIntentActivities(mainIntent, 0);
    for (ResolveInfo app : pkgAppsList) {
        if (app.activityInfo.packageName.equals(packageName)) {
            return app.activityInfo.loadLabel(context.getPackageManager()).toString();
        }
    }
    return null;
}

Below method will help to get the app icon using package name,

private Drawable getAppIcon(String packageName, Context context) {
    Drawable appIcon = null;
    try {
        appIcon = context.getPackageManager().getApplicationIcon(packageName);
    } catch (PackageManager.NameNotFoundException e) {
    }

    return appIcon;
}

Below method will help to get the list of installed application.

public static List<ApplicationInfo> getLaunchIntent(PackageManager packageManager) {

    List<ApplicationInfo> list = packageManager.getInstalledApplications(PackageManager.GET_META_DATA);

    return list;
}

Note: above method will give the launcher application too.

Below method will help to hide the app icon from the launcher.

public static void hideLockerApp(Context context, boolean hide) {
    ComponentName componentName = new ComponentName(context.getApplicationContext(),
            SplashActivity.class);

    int setting = hide ? PackageManager.COMPONENT_ENABLED_STATE_DISABLED
            : PackageManager.COMPONENT_ENABLED_STATE_ENABLED;

    int current = context.getPackageManager().getComponentEnabledSetting(componentName);

    if (current != setting) {
        context.getPackageManager().setComponentEnabledSetting(componentName, setting,
                PackageManager.DONT_KILL_APP);
    }
}

Note: After switch off the device and switch on this icon will come back in the launcher.