Dear Nishit,

This is because of the tab - ordering is not setted properly,
You can set the tab ordering at the design time, it will be
better for you to set the tab ordering listwise that you can set
from the Option from the Tools menu of the System menu,

You can set the order accordingly and also please check whether
the container where your object is located is in Back

I mean to say that the object should be in the bring forward mode
and the Object should be in Backmode.