In magento 2, Admin session is set 900 seconds. If need to change this value, please follow the below steps:

1) Go Stores->Settings->Configuration->Advanced->Admin->Security->Admin Session Lifetime (seconds)
2) Change 900 to 3600 seconds ( 1 hour )
3) Then click 'Save Config' Button
How do run security patch in magento ?

1) Download security patch what you want to install from https://magento.com/tech-resources/downloads/magento/
2) Place security patch in root folder
3) run command "sh security-patch-file-pth" ( for ex: sh PATCH_SUPEE-9652_v2-2017-02-07-01-18-38.sh )

if need more details, follow the below link

http://devdocs.magento.com/guides/m1x/other/ht_install-patches.html
Reference: http://freegento.com/ddl-magento-extension.php
Please follow the below steps :

1) Add the below script in the app/design/frontend/your theme/default/template/catalog/product/list/toolbar.phtml

<script>   
    jQuery(document).ready(function(){
        if(!jQuery('#current').length){
           
            jQuery("body").append('<input type="hidden" name="current"  id="current" value="1" />');
            jQuery("body").append('<input type="hidden" name="next"  id="final" value="<?php echo $this->getLastPageNum();  ?>" />');
           

            jQuery(window).scroll(function(event){
                setTimeout(function()
                {
                    var current_val=parseInt(jQuery("#current").val());
                    var final_val=parseInt(jQuery("#final").val());
                    var next_val=parseInt(current_val)+1;

                    if(final_val>current_val){
                        jQuery("#ajax-load").css("display","block");
                        jQuery.ajax({
                            url: "<?php echo $this->getPagerUrl(); ?>?p="+next_val,
                            async:false,
                            success: function(html){
                                var $result = jQuery(html).find('.products-grid').children();                   
                                jQuery(".products-grid").append($result);
                                jQuery("#ajax-load").css("display","none");
                                jQuery("#current").val(next_val);                               
                            }
                        });
                    }
                });
            });       
      }
               
    });
</script>

2) Add image tag to show ajax loader in the app/design/frontend/ultimo/default/template/catalog/product/list.phtml path

<div id="ajax-load" style="display:none"><img src="<?php echo $this->getSkinUrl('images/ajax-loader.gif', array('_secure'=>false)); ?>" /></div>
Reference : http://excellencemagentoblog.com/blog/2012/12/15/magento-multiple-website-login/