Are there server with rank limit in battlefield 4

It is the zeroing mechanism. This means that if you have it zeroed at 500m, the cross-hairs are dead on at 500m. This allows you to make distance shots much easier. If you were to zero the scope at 500m and shoot at a target at 100m, your shot would hit much higher than your cross-hairs. Previously, your only option was to compensate for bullet drop by aiming high and guessing between mil dots, which made distance shots on moving targets much more difficult. If you have your scope properly zeroed, now you can just offset the horizontal reticule the appropriate lead for motion.

bobfet1 already said it:

It doesn't look like there is a good way to self-cast an ammo pack.

You can adjust the range your soldier throws the package. If you look closer to the ground, you throw it in front of your own legs. This is how you can supply yourself without moving. Keep in mind that you don't have to stand exactly on your supply, it has a small range. Others, by the way, can also get supplied by this, so if you want to supply only yourself, keep in mind you need a little distance to your mates.