Can we turn a fixie bike into a freewheeler?
You can buy a flip hub rear wheel where one side is fixed, the other free (Some bikes even come with them). You just take the wheel off, flip sides and put it back on. Brakes will depend on the frame but most frames allow for the installation of brakes. For the rear brake, you'll just have run full cable housing along the frame with either wire ties or cable clamps.