@ kubbos: i just saw your question - why didn't you first ask here? See how simple your solution is? And it could have cost you hundreds of dollars... This is the beauty of Zencart - a great community always willing to help out. Sorry I wasn't so direct on FL, i didn't want to get banned... But you got the point.
For the shop1.com and www.shop1.com - exbm told you what to do. But, if you for some reason don't want to utilize a 302 redirect, you can always copy your www.site1.com_config.php and rename that copy to site1.com_config.php
And question 3 - i think it's the same thing, but really don't know.