Where can one download Halo trial version from?

It is good to hear that you're interested in Halo. Here's some basic facts about the game. Halo is a science fiction video game franchise created by Bungie and owned and published by Microsoft Studios. The series centers on an interstellar war between humanity and a theocratic alliance of aliens known as the Covenant. The Covenant worship an ancient civilization known as the Forerunners, who perished in combat with the parasitical Flood. Many of the games center on the experiences of Master Chief John-117, a cybernetically-enhanced human super-soldier, and his artificial intelligence (AI) companion, Cortana.

Getting to your query, there are no versions of Halo available for either Android or iOS platform as of now. There was a rumor of Bungie, the developers behind Halo, working for a iOS version of the game but it didn't materialize till date. But do not get disappointed, as game developers at GameLoft have come up with a game called Nova that looks and acts almost like original Halo game. Nova is being created to be the iOS's Halo, and like previous Gameloft titles, it is coming as close as humanly possible to Halo without being a direct copyright violation. The sci-fi shooter will have an impressive 3D engine with some of the best iPhone graphics to date, will have 12 single-player levels, and will include local multiplayer modes via wi-fi and Bluetooth.