1.The plane under consideration can achieve Mach 2.35 without external ordinance and stores. How and when 300m/s climb rate can be achieved; I don't know for sure but I do know that it will be dependent on such variables as: excess power available, time of climb (or gain in potential energy), also variation in thrust as airspeed decreases. Drag as I know is the frictional effect encountered by all objects moving in a fluid medium. In an aircraft the drag calculation can be complex due to various fluid flow effects and non-linear effects at high speeds.
2.No, for example, in the case of rockets, RoC would not tell you any thing about it's maneuverability ! Other parameters have to be observed for example turn rate in degrees per second; high velocity will of course affect g. Other than that we know that the su-27 can accomplish astonishing feats of aerobatics, for instance, the famous pugachev's cobra which baffled the Western aviation experts in 1989.
