I liked when I was tasked with "real" problems, one company paid for my services as a freelancer as part of the interview, another one "hired me" for one month

I liked when I was tasked with "real" problems, one company paid for my services as a freelancer as part of the interview, another one "hired me" for one month as a contractor and would then make me an offer by the end of this trial period. My current company made me part of the team for three days and gave me a real task but on the NDA it states they are not allowed to use the code produced during the interview process, it was a great experience and is what made me decide to join the company.