A: We would like to assist you, please contact our customer service department at 1-800-486-5256.
A: We used this to clean a dryer vent that was about 4" in diameter and about 5 feet long. We had to go from both ends to clean the whole length and used the larger brush. It is very flexible and worked well in our ducts. If I understand your situation you have several vents that are 4-5" diameter. I think it would work fine for them.
A: This product is designed to work with the dryer duct. Using it for anything other than was it is designed for is up the customer's discretion.
A: Each rod is 2 feet long. You can purchase additional rods from Home Depot. https://www.homedepot.com/p/EASTMAN-8-ft-Lint-Wizard-Dryer-Vent-Extension-Rod-Kit-60767/315232272
A: Exact length I do not know-you will need purchase the extension so you can clean it all out from the outside, I had to take off vent inside to clean the bottom.
A: Click the snap rods together and add the brush needed to the snap rod. It is recommended to use a cordless drill with 3/8 in. or 1/4 in. chuck that has an adjustable clutch to assist in cleaning out the dryer vents. Please contact our customer service department at 1-800-486-5256 if further assistance is needed.