jats:titleAbstract</jats:title> jats:pWe present a high-resolution kinematic study of the massive main-sequence star-forming galaxy (SFG) SDSS J090122.37+181432.3 (J0901) at jats:italicz</jats:italic> = 2.259, using ∼0.″36 Atacama Large Millimeter/submillimeter Array CO(3–2) and ∼0.″1–0.″5 SINFONI/VLT Hjats:italicα</jats:italic> observations. J0901 is a rare, strongly lensed but otherwise normal massive (jats:inline-formula jats:tex-math

</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> mml:milog</mml:mi> <mml:mo stretchy="false">(</mml:mo> mml:msub mml:mrow mml:miM</mml:mi> </mml:mrow> mml:mrow mml:mo⋆</mml:mo> </mml:mrow> </mml:msub> mml:mrow <mml:mo stretchy="true">/</mml:mo> </mml:mrow> mml:msub mml:mrow mml:miM</mml:mi> </mml:mrow> mml:mrow mml:mo⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> mml:mo∼</mml:mo> mml:mn11</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaca46bieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) main-sequence SFG, offering a unique opportunity to study a typical massive SFG under the microscope of lensing. Through forward dynamical modeling incorporating lensing deflection, we fit the CO and Hjats:italicα</jats:italic> kinematics in the image plane out to about one disk effective radius (jats:italicR</jats:italic> jats:sube</jats:sub> ∼ 4 kpc) at an ∼600 pc delensed physical resolution along the kinematic major axis. Our results show high intrinsic dispersions of the cold molecular and warm ionized gas (jats:italicσ</jats:italic> jats:sub0,mol.</jats:sub> ∼ 40 km sjats:sup−1</jats:sup> and jats:italicσ</jats:italic> jats:sub0,ion.</jats:sub> ∼ 66 km sjats:sup−1</jats:sup>) that remain constant out to jats:italicR</jats:italic> jats:sube</jats:sub>; a moderately low dark matter fraction (jats:italicf</jats:italic> jats:subDM</jats:sub> ∼ 0.3–0.4) within jats:italicR</jats:italic> jats:sube</jats:sub>; and a centrally peaked Toomre jats:italicQ</jats:italic> parameter—agreeing well with the previously established jats:italicσ</jats:italic> jats:sub0</jats:sub> versus jats:italicz</jats:italic>, jats:italicf</jats:italic> jats:subDM</jats:sub> versus Σjats:subbaryon</jats:sub>, and jats:italicQ</jats:italic>'s radial trends using large-sample non-lensed main-sequence SFGs. Our data further reveal a high stellar mass concentration within ∼1–2 kpc with little molecular gas, and a clumpy molecular gas ring-like structure at jats:italicR</jats:italic> ∼ 2–4 kpc, in line with the inside-out quenching scenario. Our further analysis indicates that J0901 had assembled half of its stellar mass only ∼400 Myr before its observed cosmic time, and the cold gas ring and dense central stellar component are consistent with signposts of a recent wet compaction event of a highly turbulent disk found in recent simulations.</jats:p>