Thanks for the follow-up @
BruceMetras
One Second folding bike's design for size 14" is very nose-heavy, especially at its handlebar's default position(forward), which is unsafe. I tried to rotate the handlebar backwards to the closest position to seat. In addition, I installed a layback seat-post in order to shift the center of weight backwards. After that the handlebar didn't feel close enough to the seat. That's why I flipped the stem. That link you provided shows 16" bikes. They are less nose-heavy, but I would still use a lay-back seat-post and rotate the handlebar to 'top' or 'backward' position instead of its default 'forward' if I had one. I won't have to have the stem facing backwards though.
As for the part you found, I misunderstood and thought you meant to mount the handlebar directly on that without using my current steerer-tube. Therefore, no daisy-chain would be used. Now I know that you wanted me to replace my current adapter with the part you found. In that case, I need to know exactly how long each side of that part is. To fit my bike, the 22.2mm side cannot be too long and 28.6mm side cannot be too short comparing to my current adapter. I feel that SpeedPark 2052-594 is the right size. Isn't it same as what you found just different in size?
Once I successfully raise the handlebar, I will be able to have the stem facing forwards again.