Renting a car is highly recommended as public transport in the area is expensive and very limited. This also gives you the freedom to explore the serenity and charm of Tuscany.

Yes, Italy does have Uber, but it doesn't operate throughout the entire country. Uber only operates in major cities like Rome, Florence, Milan, and Naples. To get around smaller towns, such as Siena, a rental car, bus, or taxi will be needed.

Yes, breakfast will be provided everyday in the main restaurant of the villa from 8am-10am. Breakfast will include coffee, pastries, eggs, meats, fruits, bread 

A two prong plug adapter will work just fine for nearly all small electrical devices designed to run on dual voltages. This means all recent laptops, tablets, and phones, most recently produced battery chargers, and many small, electrical gadgets, especially those designed for world travel. Italy's sockets are desinged to supply 220 volts of electricity, unlike the 120 volt outlets we are used to. To use applicances that are designed to run only on 110-120 volts, such as a hair dryer or curling iron, you will need a power converter. 

It depends on the type of train. The two train companies that are most popular in Italy are Trenitalia and Italo. Italo is only high-speed trains. Trenitalia has high speed (the Freccia lines like Frecciarossa, Frecciabianca, etc), and normal speed (Intercity, and Regionale).

For normal/standard regional trains like Trenitalia Regionale, you do not need to buy far in advance. The prices for Trenitalia Regionale trains will not increase closer to departure date, and they rarely sell out (however during peak season it’s possible).

For high speed trains (Italo or Trenitalia Freccia lines) and Intercity trains, you should buy tickets in advance. Tickets can sell out, and the prices will increase closer to the departure date. Note that tickets are usually released a few months in advance.