sticky bit
 

can sticky bit of a file be set for only a specific type of users(like for group or others ???

What are you trying to achieve with the sticky bit?

nothing....

just trying if it works....

what ab if I want to do this on a directory ??

Well ... if there's not actual intention/need there, why don't you
just go and experiment with it?

I hv been trying a lot of options...but it's not working

$chmod +t dd
it works fine...

but when I try
$chmod o+x dd
it works fine...but i don't find any difference

when I try
$chmod g+x dd
it's nt working

And again the question - what are you expecting to happen?
What's the desired result, what exactly "is not working"?

sorry I mistyped

$chmod +t dd
it works fine...

but when I try
$chmod o+t dd
it works fine...but i don't find any difference

when I try
$chmod g+t dd
it's nt working

/me shrugs and walks away

Do a quick search on setuid, setgid, and sticky, and do a little reading. You might also consider telling us what "it" is and how you perceive "it" to be "not working".