There were some massive changes after the revamp, so I'll give a poke at the questions too, Picchuu pretty much has them answered so I'll only answer the things that were changed.
1.2 All the base classes (Cleric / Warrior / Mage / Thief, including future classes such as DollMaster, etc) have "Universal Skills". These "Universal Skills" can always be learnt and advanced even if you pick a different advanced class in the future. Infact as you level you come across new Universal Skills up to level 60 (since that is the cap), besides that you have talent/skill tree's gained for every job advancement, and you get one every 15 levels. A mix of Universal Skills, and not having enough skill points to max every single skill in all the tree's allows for huge hybridization and unique builds.
1.4 Here's the chart, there's different advances for even you're life class, keep in mind some battle classes are restricted to some races, humans can play everything.
2.3 Yes there were a couple of status ailments, i.e debuffs
2.4 There are a whole load of stats
2.5 Yes, in fact it seems like a couple of weapons were added in KR LO including axes that affect speed/damage, classes have passives that can also effect the weapon, including speed, heal rate, damage, etc etc.
3.1 It seemed like there was something more than just stat additions, you may also combine cards now and do a couple more things with multiple cards.
4.1 Every continent (which consists of around 4+ maps) is Open World. To travel between continents there is a short loading screen. You can even travel by boat/sea mounts on some continents to get to other parts of the continent (i.e Aria Island). But pretty much every map in a continent is connected by such things as bridges and caves, and not loading screens. There are even open instance dungeons where you don't have to be in a party and can see other players and even create parties in there.