1. Yes. You can assemble as many parts as you want, as long as they fit in the area B
2. Box measures are for each individual support.
3. Deck must run over entire span of the bridge meaning that it has to be at least 5m long and the box with dimensions of 500×500 mm must be able to cross the bridge at deck level as shown in rules. You can make deck level wider or narrower as long as the box can cross the bridge.
4. Yes, ratchet wrench is allowed.
5. Yes, it counts as one element.