we get the request to share papers, what is allowed to share with these requests. what can we share without violating copyright policy of various journals
Prateek - if you mean personal requests from individuals - then that is fine to share with them. The greater the number of people you give access to, at the same time, the more likelly you will be to breach copyright.
It depends on the rules of the journal, so be sure to read the copyright rules of each individual journal in the instructions to authors.
An Open Access article can usually be shared publically. Some journals allow you to share a "pre-press" version of your paper. Some journals prohibit posting any version on ResearchGate or other public platforms. As Dean said, private sharing to individuals is generally OK.
For open access journals, it is better to share the link of the document instead of the actual document itself, to be on the safe side. For other journals, may be the starting 3 or 4 pages can be shared instead of all pages.
I usually recommend asking the journal. Send an email to the editor asking him/her, can I share parts or the whole paper with others. Some journals, usually highly cited journals, will not recommend this. You have to listen to them.