Can I plug the 4.5" lead cord into another extension cord?
Sure! But ensure your convenience, please make sure your desired installation location is within about 40" of the nearest receptacle.
Can I lock the cord at desired length any time not through adjustable stopper?
Yes. Make sure youre pulling out the desired length and returning a short length of cord into the reel until you hear a series of clicks from Ratchet Mechanism and stop within those clicks, otherwise it will retract.
What is referring to slow retract feature?
The retractable extension cord does not have any whip action rather it is a slow and very smooth retraction speed which lowers the risk of any injuries.