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.
No. Turkey requires a separate visa since is not part of the Schengen Area (assuming you are from a country that requires a VISA to enter Turkey). Schengen visas are not valid in Turkey.
Yes, You need a separate visa for Turkey. Turkey is not part of the Schengen Area. Schengen visas are not valid.
No, a Schengen visa is not valid for Istanbul. Istanbul is in Turkey, and Turkey is not part of the Schengen Area.
Yes, with Schengen visa you can enter in Croatia.
No, Turkey is not part of the Schengen Area. A Turkish visa is not valid for any other country.
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.
Surely
Yes . There are no border controls between France and Monaco, so a Schengen visa is valid.
Yes,Both Switzerland and Germany are members of the Schengen Area. A tourist visa for one Schengen country is valid for all Schengen countries.
Yes.If you need a Schengen Visa it applies for all Schengen countries, this means that you can then travel freely within the Schengen area as long as your visa remains valid.
Belgium was one of the founding members of the Schengen area, and still is part of it. So yes, if you need a visa for Belgium it will be a Schengen visa, and if you have a visa for the Schengen area, you can visit Belgium.
Turkey and the EU have recently (December 2013) concluded the early steps to form a roadmap to VISA free Schengen Zone entry. However, there are a number of issues that Turkey must rectify before its citizens will have VISA free entry to the Schengen Zone, such as asylum laws. It will likely be several years, at the very least, before VISA free travel for Turkish citizens in the Schengen Zone is even a possibility.