Steelshanks' Reserves
Text:
Army, House Bolton
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During the challenge phase, the active player gains control of Steelshanks' Reserves.

i just want to know can the controller of this card control this card again when challenges Phase ends or when dominance phase starts???

Not without some additional card effect that would allow him to do so. After the challenges phase, Steelshanks' Reserves remains under the control of the last active player until the next challenges phase when a different player becomes the active player (or before that if some other card effect puts Steelshanks' Reserves under the control of somebody else).

(3.26) Duration of Control Change
Unless otherwise stated (for example, with a
specified duration), the change of control is
permanent until the card that switched sides
leaves play or control of the card switches
again via a card effect.

is "during the challenges Phase" not the "specified duration"??

Nope - it's not a duration, it merely specifies when a control change can happen.

A specified duration would be "until the end of the phase" or "until that player is no longer the active player." But the word "until" would be involved.

In the context you're looking at, "during the challenge phase" is a play restriction on the passive effect, not a duration on it. It could say "if it is the challenge phase," and absolutely nothing would change.