Verified answer

Does study start at 8 o'clock? (Is study from 8 o'clock on?)

This is a kind of question that leaves much to be disired. Because its topic is "benkyou" (study) wa.... is Study .... from 8 o'clock? The grammar of this sentence is that Topic WA explaination of (topic) (desu is then the polite ending) ( ka makes it all into a question.) So, what I am saying that this sentence could mean something else not within the context of the sentence.

Some things we can rule out perhaps. A period of eight hours in Japanese would be expressed differently. For example: eight hours as a period of time is hachi ji kan. And, if it were hachi ji kan then it seems that benkyou might be benkyou shite iru or benkyou shite ita to be studying ....

kara is "from" basically but it can be used to express the idea of a reason for something. "because"

tsukareta! benkyou wa hachi ji kara desu ka? I am tired. Because you studied from 8 o'clock?

Really this seems a little far-fetcher but withing the realm of possibilities.

Anyway, Good Luck with your sentence