Which language is need the most to develop IOT applications and solutions?

Answer 1

Raspberry Pi, Swift, java, python c# depending on the basis of platform

Answer 2

what's the iot platform you are using?
how is the iot device accessed?
AFAIK there is not a standard yet and the way to implement an IOT depends on the device used.
Server side scripting is necessary and it depends on how you implement access to the iot device: rest api/socket connection/http requests...

Answer 3

python,c#