You can definitely shoot at those ranges without adjustment but you will be .73in high at 25 yards and 4.54in low at 75 yards zeroed for 50 yards. That is what Chairgun says for my FX500 using JSB Exact Kings at 890 fps. Have fun, Scott
I doubt it-typically your pellet's arc will cross the line of sight twice, once at a near distance and once further out, unless you zero for the top of the pellet's arc. Factors like the height of you scope above the bore and your pellet's velocity and BC will come into play here.
Here are a couple diagrams. They pertain to firearms but airguns do the same thing.