Hi,
Yes, CleanMart is compatible with VM2.6.6
Indeed, official VM2.6.00 and VM2.6.6 are almost identical in the front-end. There might be some changes in the backend of Virtuemart, but changing the backend won't affect our template's compatibility. (Because our template is only effective in the front-end)
By the way, i didn't understand what you meant with this:
After updating to 2.6 VM can not find the item you want to change most of Tutorial 2.
Possible ?.
Regards,
Support