1. It'll work, but you'll only hear Track 3 through Track 4, so the mix of reverb and voice will depend on plugin settings. I think normally we'd also send Track 3 to Track 1. Then you set the reverb plug to be 100% wet. Then you can use the track faders to adjust the mix.
2. Master/Parent Send should be enabled on Track 1. You want that disabled on every other track, of course.
3. LOL. No. There are good reasons for it sometimes. It's definitely worth doing just so you get a better understanding of how routing works. This basic idea comes into play in all different ways sometimes. Figure out how and why this works so you can stop coming to ask us every time you want to send something to something else. We're happy to help, but you need to get familiar and comfortable and confident on your own.
Course, the whole thing would be a lot easier if you make Track 1 a folder and enable all the Parent Sends. Then the only send that you actually have to make yourself is from 3 to 4. The other tracks still send to track 1, but you don't have to do the work to assign the send.
4. OK