"How long" AND "how much longer"?

Use "B" when you are on route to California. Use "A" when you haven't left yet.

No, they do not mean the same thing.

Change the sentences to baking times for a cake and you will understand better. Assume that a cake requires 45 minutes to bake and the batter is put into the oven at noon.

"How long will it take to bake the cake?" The time the cake is put into the oven is irrelevant. No matter what time you put it in, the baking time remains the same: 45 minutes.

"How much longer will it take to bake the cake?" The time left to bake the cake depends upon what time from noon to 12:45 PM that the question is asked.

The second example indicates that you are traveling and is somewhere on your way to California and asking. Or you have a place to compare distance to.

Your'e welcome.

the answer is B. how much longer till.
u usually say "how long" when referring to the countable length of something. like how long is the class, or how long is the couch.

how much longer is like from where i stand now, how much more.
so there there is this line

A _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _B

and you are at this point in the line

A_ _ _ _ _x _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _B

you will use the phrase how much longer to say how much longer will it take to get to B

you would use them depending on the content of the conversation. how much longer to cali than nevada? you wouldnt say how long to cali than nevada.