Abdulla,
Thanks for the question and good luck on the segment. I’ll try and be brief with some (hopefully) useful answers.
Training
I’m happy to hear you’re not participating for this race and asking for prep ideas now, as it’s too late to adequately prepare now 
I suspect most athletes will train like triathletes, e.g. lots of time spent running, cycling, and swimming, though most would shift proportionally more time to running given the “over”-representation of running in the event. Most of this training would be “low and slow” (zones 1 and 2) with some exposure to faster tempo work (z3). I suspect those with access to similar terrain as the race would use that as well rather than pounding out laps in the pool or around the track.
Muscle strengthening activity before, during, and after the preparatory period would also be the norm for most, as improved muscle strength has repeatedly been shown to improve endurance performance and reduce risk of injuries.
Nutrition
This is the highly variable, as the two biggest considerations are not necessarily aligned. First, fueling “needs” of ultra-endurance events to preserve body weight and subsequent muscle performance are very high- higher than really any sort of energy expenditure that could be sustained for long periods of time. The Tour de France has been called an “eating contest on wheels” to reflect the energy demands of the event and recovery from it.
We know that fueling endurance athletes during the event with energy rich foods, namely carbohydrates +/- essential amino acids +/- caffeine improves performance, but the amount and types of foods consumed are almost entirely dictated by the individual’s GI tolerance and preferences. There’s a huge chasm between what people can and will consume during an event. GI upset is a big no-no, so some of training typically involves acclimating to eating during the event. In this view, various supplements, gels, drinks, and non-traditional foods can be useful for portability, digestibility, and preferences.
Recovery
There’s no secret sauce here, e.g. ice baths, foam rolling, stretching, massage, and so on don’t really have solid evidence for improving recovery from events like this (or really anything). That said, an event of this magnitude would ideally be followed by off season training, where the programming shifts away from sports specific preparation, to restoration and general physical development. Some people may take time completely off training, whereas others won’t. It’s mostly personal preference, but time off (vs not) for a few weeks is inconsequential in the context of a training year.
For an endurance athlete, this means a marked reduction in sports specific conditioning, and inclusion of other modes they don’t normally do, plus usually an increase in resistance training, all of which starting at low intensity and low volume, gradually building up over time to the correct training load for the individual, and ultimately being reflective of the competitive schedule.
Hope this helps.
