I can address only England after the Conquest, especially in Henry II's time. (The Conquest introduced a lot of French ideas and practices; before that, I gather that there were lords of various types but otherwise I wot not.)

The answer to each question is "it depends". More generally, for most questions about the Middle Ages, the most likely answer is "it depends".

(1) An example to illustrate the broad range: In 1166, Henry II ordered an inquest of all the royal tenants-in-chief (those who held any land directly of the king), to list how many knights they owed in war, their sub-tenants, and the knight service owed to them by their sub-tenants. (Tangent: They didn't have to have any relationship. The required service of a fief was more or less fixed, and the number might have been more or less generous as the original grantor saw fit. A lord might be able to make more of fief than their overlord had thought. Or worse, might not be able to support as many knights on their fief as their overlord had thought, requiring them to hire mercenaries if their knight's service was called to the overlord's banner.)

The returns are known as the Cartae Baronum. The humblest had returns like

To his dearest lord Henry, king of the English, William son of Robert sends greeting. You should know that I hold of you the fief of one poor knight; and I have not enfeoffed anyone on it since it is barely enough for me, and thus my father held it. Farewell.

But towards the upper end, Earl Ferrers owed the service of 60 knights in war to the king and had enfeoffed 69 1/3. (A knight's fee was probably more like a unit of accounting by then. Someone holding a fief in England usually had a requirement ) The archbishop of York had fiefs returning 43 1/2. Richmond had a value of 13 knights' fees. And everything in between.

(2) If you were really lucky, you had a written and sealed charter along the lines of "I, N., for the love and service given by M., have given and granted to M. and his heirs, and by this my charter confirm, the manor of Whoville with its fields, with the presentation of its church, and the mill of the manor, and ...", with a nice neat listing of all your stuff.

But that's not so great. Charters could be lost. There could be forgeries. The farther back you go, the less literacy there was, so often there wasn't a charter. You were depending on the memory of old witnesses to the act, and maybe they disagree or don't remember the details, or maybe "my father held it for time out of mind" versus "we have been disputing your claim on this field and we have these judgments". And anyway, English charters tended to "and by this my charter confirm" -- the real action was a lord, often in his court, giving the stuff, and the charter was just a receipt, the gift card on the present. And even if you had it in writing: what were the exact borders of the fields of the manor of Whoville?

So good Lord did they ever have land disputes out the wazoo.

One traditional means of resolving it: a little private war. Using force to reclaim what was rightfully yours was considered (ceteris paribus) to be legitimate. Kings didn't like internal war for obvious reasons, and English kings were unusually strong unusually early.

If you were a goodboye and wanted law, well, good luck. It would be judged in the manoral court of the common overlord. The procedures were long and laborious, and the evidence was variable and uncertain. And if one was a royal favorite, the king might slam his thumb on the scales of justice.

Henry II made several major advances in the law. He strengthened the writ of right, the king commanding such-and-so a lord to do full right in the case: he emphasized that no proceeding about a free man's land could proceed without a royal writ of right, and devised a procedure to revoke the case to the sheriff's court if the judging lord failed to proceed. He then decreed (1166?) that a disseisin (seizing land and kicking out the current holder) "made 'unjustly and without judgment' was to be treated as a breach of the king's peace, punishable in the same way as 'pleas of the Crown'". (W. L. Warren, Henry II, p. 337, ch 9.)

Most importantly, he devised a quick means to at least get the kicked-out guy quick restoration of the land and its revenue. The writ of novel disseisin caused the empanelling of a jury, who were asked "First, had the plaintiff, as he alleged, been disseised of the freehold in question, unjustly and without judgement, within the time limit laid down? Secondly, did the person who was alleged by the plaintiff to have committed the disseisin in fact do so?" If so, the plaintiff got the disputed land. The importance is that it didn't have the laborious procedures of the customary law. Due to the time limit, it had to have been within the last few years, so it was easily in anyone's memory. The jurors were those of the neighborhood chosen specifically because they knew the answers. Unlike the customary procedures, it could proceed if the defendent didn't bother to show up or answer.

(to be cont.)