Q1: I think the best method for finding the gradient descent of this chart is checking the amount at the center point first then go up a bit, check there, then after go right and left and check there, now repeat this at the bottom as well. By the time you do this, you should definitely be able to find a point close to 3 then find points around that central point till you get a point below 3 this should only take roughly 8-10 dots. Although sometimes it might take 11-12 dots.

Q2: The method I developed also works for the limited mode, but I also have a more efficient method I used to find it much faster. Check where you start, then go up a bit, check if that one is above 20, then go down and check if that is below 10 check points there, but if it is below 20 you have to be close so check the points around there and you will be able to find it faster. Also if it is closer to the middle then branch out and form a horizontal line and if one side is closer than the other use that side and start searching based on the top and bottom you will be able to locate which one is going to be closer to the gradient descent. Using this method you should find a point within 6-10 dots on roughly 20 attempts. I only failed once with this method and found the dot usually within 6-8 dots.

Q3: I got a lot of insights, not much feelings after I figured out this method. Using this method the insights I got were to first always try in the unlimited to find a method, then go over to the limit to try out your method. If that didn't work try to find a different method or you can change up your method to make it more optimized.