purchase limit per user of each item

All my problems from above are solved

Because I use hikamerket, I can create product templates.
In the template I've set the quantity limit to 1 per order.
Then, from the Hikamarket settings, I set as the default template the template I created. Now all products that are hauled by users have this limit.

For the second problem, with the "bug" in the limit system, all I did was to go in Joomla 3 admin mentu to:
Extensions > Manage > Database
And here was a message saying that my database is not up to date. Just hit the Fix button in the Left uper corner.