Hello Francesco,
> 1) [...] Since in the calculation algorythm the OfferRule is checked at step 1b while the usual BookingRules are checked at step 4a, this should force the usual BookingRules to exist only if more restrictive.
We, as server, do not perform any check in this order. Simply if there are two or more disjointed restriction rules, the rateplan is accepted but it will never be fulfilled (=> empty intersection).
> 2) [...] When this case occurs (that means that the RatePlan allows children of any age < adult threshold), how can the children-AdditionalGuestAmount elements be consistent?
We considered the word "consistent" as synonym of "coherent". So these fields may not be strictly equal but they shoul mean the same thing.
Therefore your final interpretation is equals to the ours.