How many day the trip Hanoi – Sapa –MucangChai-Hanoi? How far is the journey?  What is the road condition like?

In order to visit  Mu Cang Chai< – >Sapa from Hanoi, you need  to spend at least 4 or 5days.

From Hanoi, you firstly, you should go to Mu Cang Chai (300km) then go directly from Mu Cang Chai to Sapa ( 160km) and the road is quite good condition and most of road is mountain road.
Here is brief itierary:

Day 1: Hanoi – Nghia Lo
Day 2: Nghia Lo  – Mu Cang Chai.
Day 3: Mu Cang Chai – Sapa.
Day 4: Sapa – village de Vu Linh
Day 5: Vu Linh – Hanoi

Hope it will help!