Regarding to Mig-29, I still think Russia should keep its design to continuosly modernize and upgrade further (like F-16 family) instead of launching Mig-35. Don't get me wrong, I have nothing argument with Mig-35's performance but just think that Mig-29s with all improment would be better than it.
For example, thank to the airframe design and lower thrust RD-33 engines, Mig-29s consume much less fuel than Mig-35s. With full internal fuel of ~4,500L (9-13) and 3 fuel tanks (2,820L in total), Mig-29s can fly 2,900km (3 fuel tanks contribute 1,400km). While with full internal fuel of 6,250L and 3 fuel tanks (3,515L in total), Mig-35s can fly 3,000km (3 fuel tanks contribute 1,000km). The Mig-35s is heavier, bigger, higher thrust and better thrush-to-weight ratio so consume more fuel. However the Mig-29's thrust-to-weight ratio as well as its maneuver capabilities still are well adequate for modern wars today.
What they need to do with new Mg-29s are to replace new engines (keep max thrush at 8,300 kgf), remove the auxiliary air intakes to accommodate more fuel, replace main wings to add more hard points and fuel, strengthen the landing gears and airframe to increase the external load and max take-off weight, etc. The higher used composites will help it keep the empty weight at 11 tons like the 9-13 version. With all changes, the new Mig-29s suppose to have ferry range of 3,600-3,800km. New Mig-29 also can equip AESA radar, advanced elec-optronic, ECM, targeting pod and fifth-generation weapons, etc like Mig-35s.