I don't quite get the reveal action in the ISB infiltrators side mission (Into the Unknown).

I know someone will say "do what the text says" but I find it unclear if I don't even reveal the small tiles and end caps until the heroes reach them, or do you treat them as rooms and halls. If a hall is made up of a big, and 2 small tiles do I reveal them all at once, or tile by tile. If the move down the straight hall first but the green deployment is on the next hidden small tile at the other end do I just deploy to the adjacent reveal tile?

If a space on a hidden tile would be adjacent to a rebel figure, that tile gets revealed.

This applies to tiles of all sizes.

Note that you can always deploy to the tile that was just revealed as part of the reveal rule, ignoring deployment points. (See deploying onto a tile from the RRG.) Optional deployments must deploy to an active deployment point.

See e.g. https://www.boardgamegeek.com/article/23673303#23673303

(At the moment I don't remember whether deploying to a tile needs deploys as close as possible if there is no space for the figure left. At least the latest ruling said that if one space of a large figure enters the specified tile, it satisfies the requirement.)