Magento – Remove “Upsell” tab on product page

You can try this.

<?php $_product = $this->getProduct(); ?>

<?php if (count($_product->getUpSellProductIds()) > 0) : ?>

    <!-- your list should come inside this condition-->
    <ul>
        <li>item-1</list>
        <li>item-2</list>
        <li>item-3</list>
    </ul>

<?php endif; ?>

If you have a valid product object on $_product, then getUpSellProductIds() will provides you an array of upsell product ids related to the product which holds by $_product. So what we are doing here is checking whether the array count is greater than zero. If it is yes, then shows the list.

Hope you get the concept.

The main problem with your code is that you are using ObjectManager::get().
This will always return the same instance of the class you pass as parameter. It acts similar to Mage::getSingleton() in magento 1.
For a quick fix use $objectManager->create('Magento\Catalog\Model\Product').
But this is not the proper way to do it. You should use the object manager only in factories, and even there you should inject it in the constructor. You should not retrieve the instance like you do ObjectManager::getInstance();.

You should use the product factory instead.
Something like this:

<?php

namespace YS\India\Block;

use Magento\Framework\App\ObjectManager;
use Magento\Catalog\Block\Product\AbstractProduct;
use Magento\Catalog\Model\ProductFactory;

class Upsell extends AbstractProduct
{
    protected $productFactory;
    public function __construct(
        \Magento\Catalog\Block\Product\Context $context,
        ProductFactory $productFactory
    ) {
        $this->productFactory = $productFactory;
        parent::__construct($context);
    }

    public function getUpSellProducts()
    {
        $product = $this->_coreRegistry->registry('product');

        $upSellProductIds = $product->getUpSellProductIds();

        if(isset($upSellProductIds)){

            $products = array();

            foreach($upSellProductIds as $productId) {
                $product = $this->productFactory->create()->load($productId);
                $products[] = $product;
            }

            return $products;
        }

        return null;
    }
}