1.A: Era and Zone have far more advanced weaponry than Classic. Throughout history, the victors have almost always been the ones with the best toys and strategy. Classic lacks in damage by only being able to deal 0.5 to a single Era or Zone player. A crab in Era deals 3 damage. This would immediately knock Classic out were it not for the fact that Classic has a 2k+ playercount with players being able to revive almost immediately. That said, they COULD rush but they'd also be getting closer to the opposition's high damage dealing melees. Now, that would be cool but this is an all out war. So perma-death in this case would be enabled. The pirate area of Classic also has cannons which obviously means that Classic has utilized gunpowder, although they haven't made guns. And if guns were made, they'd still be at a very poor disadvantage.

1.B: The Arquebus (14-15th century firearm) were fairly inaccurate single-shot rifles. This has absolutely no chance against an automatic rifle, even if it did the equivalent of 3 damage to an opposing player. Also Era players have waterguns and water balloon grenades that could render a whole cache of gunpowder useless. If anything, Classic would be that one player that buzzes around you trying to shoot at you with a starter pistol with a ridiculously long reload time.

2.A: Zone has 360° shooting, projectile deflecting sabers, and bots. The 360° shooting is a great advantage against most Era players. The reason being they can keep shooting from different angles, while only having to fear the spread from guns. The guns on Zone are also fairly spammy. Zone also has bots that can heal players and such. However, Zone also has some disadvantages.

2.B: In Zone ammo is free but it only spawns at random times. Let's say that all the Era combatants had unlimited ammo. They could just keep spamming without worry of running out of ammo. The playercount difference is also huge. All the normal combat rules apply with the exception of revive, so Era players would also have projectile deflecting weaponry. What can 100+ players do against 1000+ other players? The death roll on both sides would be fairly large, no doubt about that, but Zone is at a maneuverable advantage.

3.A: Most of Era's weaponry is modern-age and slightly absurd. Absurd as in Ice Cream daggers. However, these still count as weapons and deal significant damage. Against a Classic player, this would be an instant kill. Classic players only have 3 hp and even a single shot from a starter pistol would do the job. Era obviously has the weapon advantage, because quite frankly, this sort of thing's been played out through history, from the Conquistadors and American settlers, to the German colonial occupation in Africa. There isn't much to say other than the fact that a single shotgun user could wipe out maybe 4 Classic players at once.

3.B: Era has good healthcare. Like, insanely good. Burgers, candy, hotdogs, heart-shaped lights, and a healing stick (which may sound counter-intuitive since you have to smack someone in the head to heal them) are capable of restoring large chunks of health at a large rate. Era players are also capable of receiving powerups such as a speed-boost, simply from killing players. And the only way to beat them is to punch them right in the steroids.

4: Classic has the largest playerbase but is at incredible disadvantages compared to the highly superior technology of both servers. Zone and Era would be interesting due to the weaponry and maneuverable advantage on the Zone side, but also as to how 100+ players with combat bots would fare against 1000+ Era players with a ravenous lust for hotdogs.

Tl;dr: read the damn list.