The key point about "gradually" is the idea of grades, or degrees, or small steps. If someone says that "the temperature declined gradually from 20° to 10°" I have a mental image. I imagine that I'm looking at a thermometer and actually am able to notice that it is reading 20, then 19, then 18, then 17, ... then 10. But, yes, in order to do that, the temperature must decline slowly. So I would answer #2 "true."
I believe that "gradually" implies steadily--the movement is always in the same direction, without reversals. So I would answer #1 "true" as well.