Forecast constraints on the PPN parameters, combining S2 and S62 observations. Left panel: upper limit on |γ − 1| at 1σ, 2σ, and 3σ as a function of the distance, d, of the S62 plane, perpendicular to the LOS, from Sgr A*. When the S62 plane crosses Sgr A*, the upper limit on γ tends to diverge. For values of d > 0, on the other hand, |γ - 1| is bound and the limit reaches |γ - 1| ≲ 1.2 × 10⁻² (at 1σ) in correspondence with d ≈ 4000 AU. Right panel: upper limit on |1 − β| at 1σ, 2σ, and 3σ as a function, d, obtained by combining the forecast constraints on the combination, ϒ, of PPN parameters, obtained from our analysis on the S2 star, and the lensing constraints on γ forecast for S2.