Perugia San Francesco d'Assisi – Umbria International Airport (PEG) is the closest airport to Villa Apparita in Pienza, Tuscany, typically located about 1 to 1.5 hours away. Other options include Florence Airport (FLR) or Pisa International Airport (PSA).
Personal preference here! A car is totally not necessary, the public transportation is very good in Europe but if you feel more comfortable having your own transport you can absolutely choose to do so.
In some places yes! But I instead recommend downloading and using bolt. It is local to Europe and has better prices than uber. https://bolt.eu/en/
Use this to see multiple ways to get to a location using different types of public transportation. https://citymapper.com/?lang=en
Yes! New rules have been put into place that for short term visits to certain countries, you need a visa. More information can be found here https://travel-europe.europa.eu/en/etias