I run a strategy with 3 assets. 2 of the assets (Asset A & B) have daily history from 1990, whereas one (Asset C) has history from 2000.

I set StartDate = 1990 and set printf in log, however I notice Zorro also print out price of Asset C even before year 2000, by giving it the first available price in 2000.

Will Zorro continue to trade this Asset when it doesn't have a history yet? Is there a way to let Zorro skip this asset when it doesn't have a price?

Assets with no price cannot be traded. They will produce a flat line in the chart. Their first valid price can be determined from their first bar number.