Tried it, it works OK. Still doesn't work the same way you want it to.
While noone is talking, I would assume that the backend software is almost identical. Can it be better? No. So many people that don't know what they are doing try Instagress and get banned. Every ban is a strike against that IP ( noone really knows for sure). So Instagress stands a higher chance of getting your account banned, since IG is known to ban entire blocks of IP's.
No you don't need to worry about proxies, but they give you a "proxy" that could have been abused and banned several times, including right up to the moment you logged in.
No such thing, they are just as far off the ToS as you can get, they would need to be shelling out all kinds of money to IG if that were true.