Skyrmions　with　multiple　helicity　or　topology　in　centrosymmetric　crystals　are　intriguing　magnetic-domain　objects　due　to　their　diverse　dynamics　under　external　stimuli.　Here　we　illustrate　how　the　two　key　gradients　of　magnetocrystalline　anisotropy　(MCA)　and　spin　reorientation　transition　(SRT)　affect　the　skyrmion　formation　and　topology　by　Cu　substitution　in　the　biskyrmion-host　MnNiGa　alloy.　The　MCA　and　SRT　are　simultaneously　tuned　in　a　large　scope,　while　the　original　high　Curie　temperature　(T-C)　is　retained.　Detailed　neutron-scattering　studies　revealed　the　construction　of　a　noncollinear　canted　magnetic　structure　below　the　SRT　temperature　(T-SR),　which　effectively　correlates　the　SRT　with　the　evolution　of　the　MCA,　as　well　as　the　exchange　interaction.　The　Cu　substitution　raises　the　T-SR　to　merge　with　the　T-C,　and　meanwhile,　reduces　the　c-axis　anisotropy.　Lorentz　transmission　electron　microscopy　revealed　the　formation　of　stacked　biskyrmions　from　above　room　temperature　to　lower　temperatures　in　MnNi1-xCuxGa　(x　=　0-0.3)　in　the　presence　of　proper　MCA.　Micromagnetic　simulations　further　confirmed　the　great　effect　of　uniaxial　anisotropy　on　the　stabilization　of　biskyrmions.　Our　work　has　helped　clarify　the　evolution　of　magnetic　structures　and　their　correlation　to　the　SRT,　providing　an　account　of　the　effect　of　MCA　and　exchange　interaction　on　the　biskyrmion　formation.