## Remove deprecated BaseApplication and CLI classes
 - PR: https://github.com/joomla/joomla-cms/pull/42884
 - Files: `libraries/src/Application/BaseApplication.php`, `libraries/src/Application/CLI.php`
 - Description: These legacy classes have been removed.  
-  Use `\Joomla\CMS\Application\ConsoleApplication` or framework equivalents instead.  
-  **(more detail needed: migration examples)**
+  Use `\Joomla\CMS\Application\ConsoleApplication` or framework equivalents instead.
 
+Migration examples:
+- Before (legacy CLI):
+  ```php
+  use Joomla\CMS\Application\CLI;
+
+  $app = CLI::getInstance('MyCliApp');
+  $app->execute();
+  ```
+- After (ConsoleApplication):
+  ```php
+  use Joomla\CMS\Application\ConsoleApplication;
+  use Joomla\Console\Application as FrameworkConsole;
+  use Joomla\Console\Command\AbstractCommand;
+
+  final class MyCommand extends AbstractCommand
+  {
+      protected static $defaultName = 'my:task';
+
+      protected function doExecute(\Joomla\Console\Input\Input $input, \Joomla\Console\Output\Output $output): int
+      {
+          // command logic
+          return 0;
+      }
+  }
+
+  $app = new ConsoleApplication('MyCliApp');
+  $app->addCommand(new MyCommand());
+  $app->execute();
+  ```
+

 ## Move JPATH_PLATFORM constant to compat plugin
 - PR: https://github.com/joomla/joomla-cms/pull/44638
-- Description: The `JPATH_PLATFORM` constant is no longer globally defined.  
-  It is only available if the Backward Compatibility plugin is enabled.  
-  Extensions should avoid using this constant.  
-  **(more detail needed: code examples and alternatives)**
+- Description: The `JPATH_PLATFORM` constant is no longer globally defined and is only available if the Backward Compatibility plugin is enabled. Avoid relying on it.
 
+Migration guidance:
+- Detect safely (avoid notices/fatals):
+  ```php
+  $platformPath = \defined('JPATH_PLATFORM') ? JPATH_PLATFORM : JPATH_LIBRARIES;
+  ```
+- Replace direct path usage with autoloaded classes or services. For example, instead of:
+  ```php
+  $file = JPATH_PLATFORM . '/cms/application/site.php';
+  require_once $file;
+  ```
+  use:
+  ```php
+  use Joomla\CMS\Application\SiteApplication;
+
+  // Rely on autoloading rather than manual includes
+  $app = \Joomla\CMS\Factory::getApplication();
+  ```
+- If you truly need library paths, prefer `JPATH_LIBRARIES` or `JPATH_ROOT` and component-relative paths:
+  ```php
+  $path = JPATH_LIBRARIES . '/joomla/something/file.php';
+  ```
+

 ## Remove fetchExtensionCompatibility in UpdateController
 - PR: https://github.com/joomla/joomla-cms/pull/45436
 - File: `administrator/components/com_installer/src/Controller/UpdateController.php`
-- Description: The `fetchExtensionCompatibility` method has been removed.  
-  Extensions or scripts that called this method will break and need to be updated to use the new update handling logic.  
-  **(more detail needed: replacement approach)**
+- Description: The `fetchExtensionCompatibility` method has been removed. Update your integrations to use the update model and manifest constraints.
 
+Replacement approach:
+- Use the Installer Update model to fetch updates and evaluate compatibility:
+  ```php
+  use Joomla\CMS\MVC\Factory\MVCFactoryInterface;
+  use Joomla\CMS\Factory;
+
+  /** @var MVCFactoryInterface $mvcFactory */
+  $mvcFactory = Factory::getApplication()->bootComponent('com_installer')->getMVCFactory();
+
+  /** @var \Joomla\Component\Installer\Administrator\Model\UpdateModel $model */
+  $model = $mvcFactory->createModel('Update', 'Administrator');
+
+  // Refresh update information
+  $model->findUpdates();
+
+  // Get available updates and evaluate constraints (Joomla version, PHP, db)
+  $items = $model->getItems();
+
+  $app = Factory::getApplication();
+  $joomlaVersion = JVERSION;
+  $phpVersion = PHP_VERSION;
+
+  foreach ($items as $item) {
+      // Example: inspect $item->targetplatform or manifest extra fields
+      // and compare with current environment
+      // Skip items that declare incompatible constraints
+  }
+  ```
+- Alternatively, query update sites directly and parse extension manifests for `<targetplatform>` and `<updateservers>` constraints.
+