Look at the picture with the tape measure. You'll see the small pieces. They get dry and crumble. When i wash my car they go with the water as it drains.
Yes. That was clogged. Take the tape off on the left. That's the backup drain hole. I pulled the tape off and all the water drained out. As well as the one you circleed
This has been going on like a running TV series. You just started watching. Find the first season and catch up to the rest of us. You'll see why we are joking and being sarcastic.