I want to know just how hard it is or if its even possible

There are millions of people in the world.

yes its possiable i know there are a few people on this site that did it and i am on the final boss as ventus at level one on critical so it is possibile but really hard

I'm about halfway through with Terra and I just started it in KH2FM.

It's really hard but possible. You have to have a heck load of HP things though to have a chance.

I did KH1 and Ventus and Terra BBS.

Easy as firetruck.

so many ppl have lol

Yep. You're normally alright if you have the health and sometimes abilities ready to use.

i am after disney with terra,ven and aqua its possible if you use certain commands like ignite ,poison,mines and dodge and guard like really good,

Apparently it's possible, but I know it's something that I will never attempt.

I think pretty much everyone agrees that it is possible but I know from the heart that BBS isn't really well designed for a lv 1 run. You have to think, not twice, but thrice if you want to attempt so. I myself haven't think of doing it due to time restriction. But eventually I may have to attempt it and post vids. I am currently saving money for some AverMedia! Coz saying that I've beaten challenges isn't enough proof.

Um.... Its possible! You just need guts

I did! It was very, very hard. Things to remember are that the command board if your best friend. Make sure to get all of the abilities as fast as you can. Use the shot lock many times, if you're playing a different character than Aqua, make sure to get her D-Link upgraded first because she has auto life. And test around with different commands. Like Captain Hook is very vulnerable to fire commands.

anything is possible but that is going to take a very long time