How do I fix my old minibike engine?

I bought a baja mini back in 2008 and it died after a week... Now a few years later I have decided to fix it but first I need the engine to run well... this engine has several issues and at least try to answer 1...... so here we go... #1 The engine will only run if I have the choke all the way on and will die as soon as I take it off. #2 Gas will not stop leaking out of the carburetor and I have checked everything!!!#3 If I try to idle it at all it will immediately die on me#4 The rpms keep going up and down and wont stay constant unless I go full throttle!!! That is not all but those are the problems so far please answer if you know anything on how to fix it because I miss riding my minibike smoothly!