Yes a police officer can handcuff someone before arresting them and just because someone gets handcuffed or even placed in the back of a police car it doesn't mean they are under arrest or will go to jail.
There was a robbery in a town I was in one night and I actually did match the description pretty closely of the person who robbed the store.
So the police stopped me that night while I was walking and handcuffed me for around 10 minutes until they investigated the situation.
I understood why they did it because I actually was pretty close looking to the robbery suspect and they handcuffed me and did a search on me just to be safe.
I'm glad they did their job correctly and around 20 minutes later after they had let me go they found the correct person.