Sounds a lot like a test question I know... this might have something to do with giving up tea? :-D
Let's start with the three Adjectives:
Possible: Capable of happening... can happen... can exist, can be...
"Can you walk to school?" "Yes, it is possible."
"Can you fly like a bird?" "No, it is not possible."
"Can any person be president some day?" "Yes, that is possible."
"Can a rabbit be president?" "No, that is not possible.
So Possible talks about IF something can happen, can exist, can be.
Probable talks about if it maybe, could be, might be going to happen, going to exist in the future.
"Can you walk to school?" "Yes, it is possible."
"But, school is 100 miles away." "Right. It is possible but not probable."
"Could you fly an airplane?"
"Yes, if I went to flying school, it is possible I could fly an airplane.
"But, you hate airplanes."
"Yes, so it is possible for me to fly, but it is not probable. I will probably not fly. My sister likes airplanes, so she probably will fly airplanes."
Likely is the 3rd adjective... it means something has, possesses "Probable"
It is probable that I will go to school. SO
It is likely that I will go to school,
I will likely go to school.
It is probable that I will finish this answer. SO
It is likely that I will finish this answer.
I am likely to finish this answer.
Probably this answer is too long. SO
It is likely that this answer is too long.
If it will probably rain, it is likely that it will rain.
And
Possibly is the adverb. If a verb, if an action is probable, if you think it will happen, then it acts possibly... for example,
It is probable that I will sing, SO
I will probably sing.
I will loudly sing, I will happily sing, I will probably sing. They all describe how I will sing.
It is probable, it is likely to happen, that I will finish this answer tonight, SO
I will probably finish this answer tonight.
I will happily finish this answer, I will tiredly finish this answer, I will proabably finish this answer. They all describe how I finish this answer.