Similar to what NoSoap answered:
1. You can layer Opti seal if you want. 2 layers are enough to cover the entire car so there are no missed spots. Opti seal does not have any solvents in it so you could apply the second layer right after the first one. The car was usually glossy enough after the first layer for me so the second layer might enhance it a bit.
2. Yes. Opti seal is a great rinse aid. I use it to dry the car after I washed it with either ONR or Car wash.
3. Which one is the ANY WAX? Joke...You can use any wax you like on top of opti seal. Give it an hour before you do so.
4. Dont really know but I would do 2 layers of Opti seal (one after another) and after 1h a layer of wax or OPT Car wax...whichever you prefer. A nice oily wax would enhance the finish even further. Of course polishing before sealing would be the best option for glossy paint.