Making sense of the structre of a horse race historical data file

[fdsafds]

I'm trying to make sense of historical data of horse races. I'm using Basic plan.

(1) Event in this case is a horse race; and "runners" are the horses that participate is a race. Right?
(2) one line in a json file, is one "bid" or "guess", right?

(3) In most, if not all, the cases there're only 2 horses in a competition. Why? Why aren't there more?

[fdsafds]

4) In some cases the status is ACTIVE. What does it mean? It's historical data after all. Who won and who lost then?

[BetfairDeveloperProgram]

(1) Event in this case is a horse race; and "runners" are the horses that participate is a race. Right?

Correct

(2) one line in a json file, is one "bid" or "guess", right?

Each line represents a new update MarketChangeMessage (mcm). This may be a change to any of the fields within either the

MarketDefinition - (Fields containing details of the market - new market definition is published if any of these field change
RunnerDefinition - Details of the selections in the betting market
Market change - Changes to market prices, runners
Runner Change - a list of changes to runners

You can find the full fields and data specification via https://historicdata.betfair.com/Bet...cification.pdf

(3) In most, if not all, the cases there're only 2 horses in a competition. Why? Why aren't there more?

All selections that took part in a race/event are included.

[fdsafds]

Does (2) mean that the lastest line in each file is always the most accurate one? In other words, most recent, closest to the "start" one.

[BetfairDeveloperProgram]

Does (2) mean that the lastest line in each file is always the most accurate one? In other words, most recent, closest to the "start" one.

The latest line in each file represents the last (most recent) update to the market/runner information. This update will indicate the status of the market, or for the runner, the last traded price (ltp) in the BASIC data.