Does recreational use always lead to addiction?

Always? No. But everybody who is a addicted started out as a recreational user. Generally in life and in medicine you never want to say 'always', and you never want to say 'never' . There will always be exceptions. It also makes a difference what recreational drug you are talking about. Some are more likely to be addicting than others. And of course some people are more likely to be addicted than other people.
That depends ... There is a "pleasure center" in your brain designed to respond to good food, good relations, and good work. A substance or behavior that generates a more than expected reward can lead to incentive sensitization if the person is biologically predisposed to addiction. The faster the drug effect reaches and then leaves the brain, the more craving will develop, such as with nicotine or crack cocaine.