Tax refund in Paris airport, how do you do it properly?

Hi, I'm a non-EU resident, I will be leaving Europe via France next Monday and would like to know how to properly do the tax claim. So far from what I read online I will need to be at the airport 3hrs before the flight, I plan to be there at 4hrs before. I bought items from France and Italy, is it alright if I claim everything in France Airport? I did some cash claim in France previously, I was told to get the documents stamped at the airport if not I'll get charged back on my credit card am I right?

There seems to be quite alot of different company's on the tax refund document.. It is very confusing.. When I get to the airport am I able to do it all at the same counter in terminal 2?? Also, some of my purchase I asked for cash and some by credit card. Is it a mistake? I get confused by the 10.8% and sometimes 12% refund by credit card in Paris. When I'm shopping in Italy they say it's always 12%, why is it diff when in France?

If some kind soul can give guidance on how to do a proper claim it would be wonderful.

Thank you in advance.