What is the correct procedure when uncoupling a semitrailer from a tractor unit?

1. 1. Secure trailer with wheel chocks and apply trailer parking brake -> 2. Lower landing gear legs -> 3. Disconnect electrical and pneumatic lines -> 4. Pull fifth wheel release handle -> 5. Drive tractor forward smoothly
2. 1. Pull fifth wheel release handle -> 2. Drive away immediately -> 3. Let air hoses snap off automatically
3. 1. Lower landing legs -> 2. Disconnect air lines -> 3. Leave trailer unchocked on a slope
4. 1. Disconnect air lines only -> 2. Drive tractor away with landing legs up