Rarely if none at all. Women were not trained to be fighters in the medieval age because it was deemed to costly as they would be uneffective fighters against men. Religious reasons, social...
Yes, a good example would be one of the crusades, where children marched towards a war before having to retreat because of technical issues. "The Children's Crusade"
In very rare cases, a man of humble birth might be rewarded for armed service by being knighted. An interesting thought is that William the Conqueror was himself of rather unremarkable origins: his...