Questions about JobsFollow

Leveling:
For Solo:
_Monk is as easy to solo as Pugilist. Pugilist can use LNC skill to boost dmg, CNJ spell like Stoneskin/Protect as well as GLA skill to increase survivability. On the other hand, Monk has extra Weapon Skill so you have more combo in higher level.
_Lancer is much easier to solo than Dragoon. Lancer has more protection through CNJ spell and you dont use up MP as DRG/LNC as you would with MNK/PUG Fist of Fire/Earth/Wind, so you dont have to be worried about running out of MP.

For Party:
_Monk is easier than Pugilist.
_Lancer is arguably on same par with Dragoon. Lancer has less damage, but can do support at the same time. For instance, Lancer can raise when the Healer is down.

For instanced/NM/dungeon/stronghold:
_Monk is better than Pugilist. You are always in a pt, more damage is better.
_Same reason, Dragoon is better than Lancer. Also LNC/DRG can't stay in safe spot like ARC/BRD/Mages so there's not much point in supporting with Stoneskin/Protect/Raise/occasional Cure.

Class can use any skill/abilities that are cross-class-able as long as you've learnt it, no limit on level (though there's a limit how many cross-class you can equip per level). Job can only use those from two sub-classes, example BRD can only use CNJ and THM and nothing more. ARC on the other hand, can use all 7 classes. All jobs skills are not cross-class-able.