1) Borderline 2) Certainly not certain 3) Chancy 4) Conditional 5) Conjectural 6) Containing doubtful parts 7) Doubtful 8) Dubious 9) Far from a sure thing 10) Far from definite 11) Flukey 12) Fluky 13) Full of questions 14) Full of uncertainties 15) Full of unresolved questions 16) Hardly set in stone 1) Flukey 2) Fluky 3) Illegal 4) In doubt 5) Not sure 6) Uncertain 7) Unsure 
Iffy is slang for questionable, dubious, doubtful, suspicious.
Doubtful, questionable
full of unresolved points or questions: an iffy situation. · doubtful; questionable: An early decision on this is iffy.