[cheflayne]

To me, the telling factor would be the reaction to being presented with a mystery basket of ingredients and being told to make something utilizing all the ingredients.
A high level enthusiastic amateur will be excited at the prospect and jump right in; with a can't wait attitude.
A regular cook, not so much. I would expect some hemming, hawing, wheel spinning, and floundering; before action begins with a somewhat begrudging attitude.

 

[cheflayne]

What’s the difference between a professional cook and an non professional?

To me it wasn't quite clear if this was what was being asked or if "What's the difference between a high level home cook and a regular home cook?" was the question.
I kinda sorta geared my previous answer to the second question, as the first question is like comparing apples and oranges

 

[cheflayne]

I mean how hard is consitency?

If you are working saute station for example and a dish comes with a beurre rouge made to order and over the course of the evening you get 35 orders along with orders for 65 other items, all with sauces to order, and every one of those 100 orders plus 100 sauces has a sense of urgency to it as in the customer wanted it yesterday...consistency is making sure that the first beurre rouge of the evening is exactly the same as the last beurre rouge of the evening.