1 - SAD: No, because I and everybody that I know live inn a tropical country. RSI: Yes, some of my friends in the work are these problems, specially in its wrists.
2 - Yes, I make sure. I'm carefully with these things. I don't have problems for that.
3:
a - Sit leaning your back in the chair
b - Don't be working for a lot of time without rest.
c - Do some exercises between each stage of work.
d - Sleep in a confortable position.
e - Stand up and walk around, if you feel much tired of with pain.
4 - I like two movements:
a - Bend the head to the left and to the right, in many variations.
b - Hold the elbows with your opposite hands.