Magento 2 get category collection using specific controllers and category level using object manager

Magento 2 get category collection using object manager

 <?php  
 $objectManager = \Magento\Framework\App\ObjectManager::getInstance();  
 $category = $objectManager->get('Magento\Framework\Registry')  
   ->registry('current_category'); //get current category  
 $requestInterface = $objectManager->get('Magento\Framework\App\RequestInterface');  
 //echo $routeName   = $requestInterface->getRouteName();  
 //echo $moduleName   = $requestInterface->getModuleName();  
 $controllerName = $requestInterface->getControllerName();  
 //echo $actionName   = $requestInterface->getActionName();  
 $parcatId = $category->getId(); // current Category ID  
 $parcategory = $objectManager->create('Magento\Catalog\Model\Category')  
   ->load($parcatId);  
 $parent_category = $parcategory->getParentCategory();  
 $subcatId = $parent_category->getId();  
 $subcategory = $objectManager->create('Magento\Catalog\Model\Category')  
   ->load($subcatId);  
 $subcats = $subcategory->getChildrenCategories();  
 $_helper = $this->helper('Magento\Catalog\Helper\Output');  
 ?>  
 <?php if ($parent_category->getLevel() == 2 || $controllerName == 'product'): ?>  
 <ul class="sub_cat_bg navigation">  
 <?php  
   foreach ($subcats as $subcat)  
   {  
     $subcaturl = $subcat->getUrl(); ?>  
  <li class="cat_image_bg level0">  
   <a class="level-top" href="<?php echo $subcaturl ?>">  
   <span><?php echo $subcat->getName(); ?></span>  
   </a>  
  </li>  
  <?php } ?>  
 </ul>  
 <?php endif; ?>