My answer is in general, and not for that model in particular, but all but 2 is pretty general.
1 dunno about that ESC, but yes it is sound advice to always disconnect the battery when not in use. I remember years back someone didn't do it for awhile, and if I recall right their ESC started smoking. The battery is still connected to some parts, and depending on the battery(LiPo) that could cause it to discharge, and damage it. Generally it is good procedure to not be lazy, and remove the battery from the vehicle when not in use, and also while charging.
2 dunno that model
3 generally you can find the vehicles wheelbase, and look for bodies from that.
4 Those are just LED's you can either wire them up yourself if you have and soldering experience, or buy LED kits off ebay like this one
https://www.ebay.com/itm/Apex-RC-Pro...9Y1:rk:12:pf:0
5 most likely he made those using a printer with a clear sticker sheet. I bought a few a couple years back to make stickers for something else.