I put on a new dryer vent and where the old one was connected to the dryer
there is a collar on the dryer connection. This kept falling off as I put
the new vent on the dryer so I just put it to the side and did not use it.
Is this collar necessary, or is it just to help fit the vent to the dryer's
exhaust port?

I also had to use duct tape to tape the pieces together. I never used duct
tape for its real purpose of taping ducts. Will the hot exhaust air melt
the tape or loosen it's adhesiveness?

Thanks!!

Eddie G