Yes, Greece is a member of the Schengen Agreement and Schengen visas are valid.
Turkey is not part of the Schengen Area. Schengen visas are not valid.
If you have a Schengen Visa, you do not need a Visa to enter Switzerland. But, just make sure that you have this written "Schengen Estate" on the visa. It means that all Schengen countries are included in the visa. Anyway, once you enter Europe, nobody asks you about your visa or passport.
To obtain a Schengen visa, you must submit the Schengen visa application at the embassy of one of the Schengen countries, along with passport photos, your passport, and proof of health insurance. If you are a U.S. Citizen, you can enter the Schengen area for up to three months without a visa.
It depends on where you are coming from. If you live inside of the Schengen Zone, there is no problem. If you live outside of Schengen, you will probably need a new passport, especially if you need a VISA to enter Spain.
This depends on what country you are comming from. Because Slovenia is a part of Schengen regime, same rules aply as in the other Schengen countries.
No,Turkey is not part of the Schengen Area. Schengen visas are not valid.Technically speaking, it is unclear whether or not the Schengen VISA holder can enter Turkey or not. It would depend on the passport the VISA holder has and whether or not that person can get additional VISAs. What is clear is that a Schengen VISA is not valid itself for entry to Turkey.
Yes, with Schengen visa you can enter in Croatia.
No. US passport holders are allowed 90 days visa-free travel in Germany and the other Schengen-Agreement countries.
Yes. Macedonia like the rest of Greece is part of the European Union.
Although both Greece and UK are in the European Union you still have to show an up to date passport in and out of both countries.
It depends on your nationality. Switzerland is part of the Schengen Area. If you have an EU or Schengen area passport, there is no minimum validity. You can even travel to Switzerland on your national identity card, if you are from a country that issues them. If you are from a non-Schengen/EU country you need a validity of at least 3 months on your passport, and if you need a visa then you also need 2 blank pages on your passport.