Magento 1.9 Theme – Switch Between Mobile and Desktop Version

Write below code in action to set Package and theme for the action

Mage::getDesign()->setArea('frontend') //Area (frontend|adminhtml)
->setPackageName('default') //Name of Package
->setTheme('modern'); // Name of theme

The short answer here is no, though, you could drop a javascript cookie called forcedesktop and set it to true. This would be set onclick for the switcher link.

Then rewrite the design exception method to sniff for existence of the cookie:

app/code/local/YourCompany/YourModule/etc/config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <YourCompany_YourModule>
             <version>0.1.0</version>
        </YourCompany_YourModule>
    </modules>
    <global>
        <models>
            <core>
                <rewrite>
                    <design_package>YourCompany_YourModule_Model_Design_Package</design_package>
                </rewrite>
            </core>
        </models>
    </global>
</config>

app/code/local/YourCompany/YourModule/Model/Design/Package.php

<?php

class YourCompany_YourModule_Model_Design_Package extends Mage_Core_Model_Design_Package
{

    protected function _checkUserAgentAgainstRegexps($regexpsConfigPath)
    {
        if(Mage::getModel('core/cookie')->get('forcedesktop')=='true'){
            return false;
        }

        parent::_checkUserAgentAgainstRegexps($regexpsConfigPath);
    }
}