Sometime we customise code , so we need to get drop-down attribute values in custom file.

So the below code will help to retrieve attribute based on attribute id

$objectManager = MagentoFrameworkAppObjectManager::getInstance();
$attributeId = 101;
$eavModel = $objectManager->create('MagentoCatalogModelResourceModelEavAttribute');
$eavModel->load($attributeId);
$attributeCode = $eavModel->getAttributeCode();
$productAttributeRepository = $objectManager->create('MagentoCatalogModelProductAttributeRepository');
$options = $productAttributeRepository->get($attributeCode)->getOptions();


?>

<div class="field required">
    <label class="label"><?= /* @escapeNotVerified */ __('Colour') ?>:</label>
<div class="control">
<select name="product[color]" id="color" class="required-entry input-text">
<?php
foreach ($options as $option) {
    $value = $option->getValue();  // Value
    $label = $option->getLabel();  // Label              
    ?>
    <option value="<?php echo $value; ?>"><?php echo $label; ?></option>
    <?php 
} ?>
</select>
</div>
</div>

that’s it. Happy coding.