Is Code Name S.T.E.A.M. on Steam?

No. Code Name S.T.E.A.M. is not distributed on Steam, so there is no Steam Charts or SteamDB player count for it. Its live popularity is tracked here via Twitch viewership instead.

What platforms is Code Name S.T.E.A.M. on?

Code Name S.T.E.A.M. is available on Nintendo 3DS.

When did Code Name S.T.E.A.M. release?

Code Name S.T.E.A.M. released on March 13, 2015.

Code Name S.T.E.A.M.

Mar 13, 2015ShooterStrategyTurn-based strategy (TBS)Nintendo 3DS

Code Name S.T.E.A.M. — frequently asked questions

Is Code Name S.T.E.A.M. on Steam?: No. Code Name S.T.E.A.M. is not distributed on Steam, so there is no Steam Charts or SteamDB player count for it. Its live popularity is tracked here via Twitch viewership instead.
What platforms is Code Name S.T.E.A.M. on?: Code Name S.T.E.A.M. is available on Nintendo 3DS.
When did Code Name S.T.E.A.M. release?: Code Name S.T.E.A.M. released on March 13, 2015.

About Code Name S.T.E.A.M.

Launch S.T.E.A.M., an elite team of steam-powered special-forces soldiers, to save the world from an alien menace. In this new blend of action and strategy, your commandos use steam power stored in special backpacks to move into position and fire an arsenal of distinct weapons. Pick your team members and load out, then use strategy to decide the best way to approach this steampunk-inspired battlefield.

Summary via IGDB.

Code Name S.T.E.A.M. on Wikipedia

Code Name: S.T.E.A.M., known in Japan with the subtitle Lincoln vs. Aliens, is a turn-based strategy video game developed by Intelligent Systems and published by Nintendo for the Nintendo 3DS handheld game console. The story is set in an alternate steampunk-based history and features a Silver Age comic book art style and a cast of characters from across American literature and folklore. The gameplay blends turn-based strategy with third-person shooter elements in a similar vein to the Valkyria Chronicles series.

Source: Wikipedia (text under CC BY-SA 4.0).