lucy24 - 9:18 pm on May 12, 2013 (gmt 0)
Prestashop use the .html extension for product URLs and Opencart doesn't.
Oh now wait. So you're also redirecting to a different domain? In one way this makes it easier, because you don't have to keep track of rule ordering; the rewrites will happen in a completely different place. That's assuming the new domain is also on a different server, or at least in a different userspace in shared hosting, so requests for the two domains will never pass through the same htaccess.
The bad news is that WebmasterWorld doesn't write people's code for them. We're more about helping people learn how to do things for long-term benefits. You might try That Other Forum. They seem to be correct more than half the time.