Hello i will not copy and paste here "like most" of indian developer does:) that i do fully understood your task:)) and ready to go:)
But simply will write that i have been working with opencart system for about 7-8 years (cant even remember for how long) have developed extensions the ones are sold up to 300 copies. Also i do have a partner status in my country from opencart.
Do not have much reviews and tasks here completed on this website as i never needed to bid here alot:) as all my clients comes from one to another by a "word of mouth" my daily work is build custom featured for opencart , debug it , upgrade it , in simple words any task related to opencart is my field:) so let me know if you need experienced opencart developer the one is working with the system for so long that knows it as a palm of own hand:) And about your login and registration pages i can make it anyway you need. Just describe how you want it to be working:)