Thats a type of answer I wanted.
Well, ive been reading from some books and it says that in the 14th century Knights wore a mixture of chain mail and plate mail. So I guess like, if the armour was very well decorated, different types of armour they would have worn [Like, versions of plate and chain mail], stuff like that.
The type of Armour depended on the purpose, eg cerimony or combat.
In general in the later middle ages the plate armour became more common than the chain armour wich was extensively used earlier, eg. during the crusades. The plate armour oferred a better prootection but was heavier.
I'm not sure if it also affected the agility. Some Reenactors I talked to claim a well made plate armour doesn't. On there other hand, there are examples like the Battle of Agincourt where dismounted Knights simply drowned in the mud because they were unable to get up.
The lance was, beside in the turnier fights, mainly used in a cavallry charge. I supose spiked weapons like the morningstar or a battle mace replaced the use of the sword with the more widely used plated armor because unlike a sword such a weapon could penetrate the armour. However, more common was it to take the knight down and finish him off with a dagger at the unprotected or less protected parts of the armour, eg between the legs, under the axles or the viewports of the helmet.
Helbards and similar weapons were used by infantry, they have been designed to pull a mounted fighter down from his horse.
About the knights duties, keep in mind there have been knights who where rich, poverfull and important positions and, especially to the end of the middle ages, those who were poor and without much or any property. The later ones than either worked as mere mercenaries or simple criminals.
Also, as shown in the battle of Agincourt, the knights armour lost its usefullness with the widespread use of armourpiercing Longbows and crossbows. AFAIK Kights also used the battle axe. But keep in mind there have been local differences. The Lochaber axe eg wasnt used on the continent and neither the Longbow (atleast not widespread). What I can reccomend is, not specific about knights but in general about the middle ages, Ken Follets Book Pillars of the earth.