I can address the second part of your question: nobody in their right mind would try to charge through a shield wall. There are many, many problems with trying to do such a thing, but it really starts and ends with the horse. It's very hard to train a horse to ignore the basic instinct of not charging into a solid mass (sharp objects notwithstanding). What was done, if a head-on charge was desired (a rare circumstance), was to charge the horses toward the enemy line and hope the psychological pressure would cause the formation to break. It's not easy for the men in the first few rows to hold their ground with a horse charging right at them. If they were disciplined, though, the cavalry would break off, withdraw, and regroup. There are examples of heavy cavalry charging into formations head-on, but most of them don't come until much later (Winged Hussars being a notable example).

You're talking about the Battle of Hastings where the Norman Knights charged up to the Saxon shield wall and threw spears right?

From this - Weapons that Made Britain: Shields?

Or Weapons that Made Britain: Lance

Hastings isn't my area of expertise so I can't say too much on that specific battle. I've looked through the Bayeux Tapestry a bit (it's really long though) and read some articles on it but primarily with regards to the archery. I can say that the Normans had archers with them at the battle and they fired at the Anglo-Saxon lines in support of the Cavalry charges.

The way knights fought certainly changed over time. By the time of Crecy the French army opened their battle by firing a volley of crossbow bolts into the enemy ranks. They then charged with their knights at the lines with the usual result that the now injured lines would break in front of the charging cavalry and they could run their enemy down. Famously this went disastrously badly at Crecy. The Genoese Crossbowmen were ineffective (why their crossbows failed is an oft-debated and probably forever unclear topic) and were promptly run over by the impatient French cavalry. Froissart has probably the best account of Crecy, although his is directly copied from Jean le Bel (who was there) so you could always find and read his original.

If we skip ahead to Agincourt (I know I'm picking battles the Cavalry failed at..but those are the ones I know) the Cavalry was instead on the flanks of the army and charged the English Archers (who were also on the flanks) but were driven back. The bulk of the battle was actually fought on foot as the center lines collided. There are lots of accounts of Agincourt and books one it but the ones I'm most familiar are from John Keegan's The Face of Battle and Jim Bradbury's the Medieval Archer.

There's some debate among military historians as to the extent of the importance medieval cavalry. The cavalry tended to be the from the nobility and so were written about more in the accounts of battles. From the fourteenth century we have pretty good evidence to show that infantry were a huge part of medieval armies but whether that was a major change in that century, and/or the extent of that change, isn't always clear. There's still a lot we don't know about medieval warfare, sadly.