Drain damage is inevitable, but the clog-busting benefits of baking soda and vinegar aren't worth it. Your drain will eventually wear out due to the abrasive nature of baking soda. This is why you shouldn't try cleaning your drain with baking soda and vinegar.
Leaves, dirt, sticks, and trash could get into your sewer system when it rains. This could cause your drains to get clogged and your system to back up.
Not really, is the short answer. Salt by itself doesn't help your plumbing system in any way. The theory we've seen online is that because salt is coarse, it will scrape debris out of your pipes, especially if you flush it with boiling water afterward.