Can I switch from the 200k to the 120k during the 6 stages?
Yes, you can switch at any time during the 6 stages from the 200k to the 120k distance. You even will be in the official ranking of the 120k. If you start in the 200k and switch to the 120k your average time per kilometer of the stage that you ran in the 200k will be broken down to the equivalent stage of the 120k.