W. Salaam ............ Thank you bro 
A1. Security wise this route is safe, but travel at day time .... Take this route DG Khan, Rakhni, Mekhtar, Loralai, Killa Saifullah, Muslimbagh, Khanozai, Quetta.
A2. I think Car can easily come because nowadays snow is cleared from the road by concerned department, but if u have 4x4 then its better option.
A3. Antifreeze & Warm Clothers are must.