Not familiar with a Cub Cadet 147, but all the hydrostat units I've seen have a seperate lever that must be operated to move them. On sime it's between the drivers knees, but on most it is on the rear of the mower. It may be a lever to move side to side, or on some it is a knob on a shaft that goes through a keyhole type opening in the rear. to push that type you pull the knob out and hook a collar on the shaft in the keyhole.
2. Thye all will sloe down some, but slowing down to 1/3 speed seems excessive to me.
3. depends on mower, but a manual will be needed.
4. might try http://www.ihcubcadet.com