A freewheel and cassette are two different things (they are both cogsets). A freewheel has no lockring, is all in one piece, and screws onto threads on the hub, no tool needed. A cassette has a separate lockring or threaded small cog and slides onto a slotted "freehub," If you have an older cassette with a threaded small cog, then yes you can tighten it by pedaling. Otherwise you need a tool for the lockring, which has no turning force applied to it while pedaling.