Programmatically assign customer to a quote in magento

$customer = Mage::getModel('customer/customer')->load($userId);

$quote = Mage::getModel('sales/quote')->load($quoteId);
$quote->setCustomer($customer);
$quote->save();

How to copy one quote (only cart items) to other quote (only items ) in magento

$quoteA = Mage::getModel('sales/quote')->load($quoteId);
$quoteB = Mage::getModel('sales/quote')->load($userQuoteId);
$quoteB->merge($quoteA);
$quoteA->delete();
$quoteA->collectTotals()->save();
$quoteB->collectTotals()->save();

How do I add to wishlist programatically in magento 1.9?

$wishlist = Mage::getModel('wishlist/wishlist')->loadByCustomer($customerId, true);
$product = Mage::getModel('catalog/product')->load($productId);

$buyRequest = new Varien_Object(array()); // any possible options that are configurable and you want to save with the product

$result = $wishlist->addNewItem($product, $buyRequest);
$wishlist->save();

How to get (cart) items programatically shows duplicate SKUs for both the configurable and simple product in magento

As you have using getAllItems() then on for loop you need to check is it has parent item $item->getParentItemId().

foreach ($cart->getAllItems() as $item) {
    / * add this */
    if ($item->getParentItemId()) {
        continue;
    }
........
}

Check the customer password field Magento 1.9

    $email='test@gmail.com';
    $customer =Mage::getModel('customer/customer')
    ->setWebsiteId(Mage::app()->getStore()
    ->getWebsiteId())
    ->loadByEmail($email);
    $hash= $customer->getPasswordHash();

    Mage::helper('core')->validateHash($currentpassword, $hash);