There is no general answer: it depends on the copyright transfer agreement you have signed, so you should check your e-mail and / or the journal web site to look up the text of the agreement you have signed.
Anil Kumar Please have a look in another thread. RG lost the case against leading publishers. Our group received numerous legal mails from Elsevier to remove full text from RG. We have done so.
Anil - Check out the SHERPA/RoMEO website (UK based) and look up the journal you published in. Different journals have different policies about copyright transfers, self-archiving, but you should be able to find the information you are after.
It depends on the agreement you accepted and on the copyright transfer status. In some cases, the embargo period starts immediately while in other cases you can share it entirely or partially (as publicity) for few weeks before the embargo period starts. Still, some publishers (i.e. Springer) allow a read-only version to be publicly accessible. Regards