Please advise whether any kind of Trust is required for user provisioning from one forest to another one. If not how the AD management Agent identify and connect to the Target Forest domain controller. What information has to fill Forest and Domain fields in AD management agent connectivity tab. whether credential given in the target AD management agent authenticates to the target forest domain controller without trust.

MA uses an account from that Forest. All you need is the IP address of that forest. I don't believe you need trust at all, but at the very worse case a one-way trust.  When you setup the MA, enter the IP address, since the DomainName may not work, provide the user ID and Password from that Forest, and you will get the confirmation if it worked or not.  Make sure user has access to Replicate Changes, Delete, Create users and groups.  See the guide for AD MA Account.  http://social.technet.microsoft.com/wiki/contents/articles/330.how-to-configure-the-adma-account.aspx