I have touched some of the points you are looking for in this answer. It is a rather large topic to address, especially with the focus on the origin of the unification process.

I must add though that, when the unification begun, Italy was not divided in city-states; those had ceased to exist essentially by the time of the French, Spanish and Austrian domination, between 16^th and 17^th Centuries. As you can see in this map, in Italy there were two independent states: the Kingdom of Naples (later Kingdom of the Two Sicilies) and the Kingdom of Sardinia. Another weaker State ruled the Pope, which included semi-autonomous administrations in the Cities of the so called Legations. A region (Lombard-Venetian) ruled directly by the Austrians. A few States under strong Austrian influence trough dynastic ties, such as the various Duchies under the line of the Po Valley and the Grand-Duchy of Tuscany.

While the focus of my answer was a bit different, I think it can help you understand the process of unification better and put it in the right time frame. I might manage to put something else together about the beginning of this unification process during the Napoleonic Wars and the occupation of Italy.

We have gotten this question in the past. Italian unification is a large and complex topic. You can read a three-year old answer by u/kieslowskifan answer here, which does a good job of contextualizing Italian unification within the narrative of post-Napoleonic european consolidation.

That answer's a bit short, but so are many of the others: the general rule is that the wider the topic, the shorter and more generic the answer will be; only with difficulty will someone find the time to to summarize a question that can full a whole book. You might be better served going directly to a book, like John A. Davis' Italy in the Nineteenth Century.