Here goes
1 Variable flap setting allows the best selection between field lenght and second segment climb limit
2 Flap setting will be determined by weight altitude and temperature on the day at that particular runway
4 Use of reverse and lenght of runway limits the use of braking.
Centre gear does have brakes.
5 Minimum has to be trip fuel required for diversion plus max 10%plus a 30 minute reverse for holding at alternate at 1500' This figure will depend on distance to diversion. Or if no alternate available fuel for 2 hours holding at destination This is referred to as island holding
6 Long range cruise for economy others as required to make up time
7 3 1 2
8 Yes KLM used a procedure on the DC10 in event of APU u/s
9 No2 eng would be the candidate for this procedure
Hope it helps