Is it possible to link the "Check-out" button on my customized Form?
Or is it possible to edit the Check - Out Form?
I already download the zip file of the 1.1.8 , how can I install it on my AbanteCart Cart?
Can I customize / add my own Payment Options?
Please do not put many questions in one post if you want to get straight answers. :-\
There are many posts and documentation that covers installation and upgrade.
http://www.abantecart.com/ecommerce-documentation/20-installation
Yes, you can add your own payments.