Dear Chaitali,
No,the non-residents are not required here to come to India for an incorporation of any Limited Company.The incorporation docuements can be signed even outside India to be filed with MCA .If they are going to be director or first directors in the proposed company then you have to suitably obatin thier DIN from the respective DIN cell of the MCA first.
As per your query no. 1 there is no restriction for any non-residents to act as promoters of the proposed comapny but you have to check from the FDI scheme and the from the FEMA aspects whether the acting non-residents which are going to be promoters of the company are not restricted to invest the fund in the proposed company.If they are then you have to suitably obtained the permission from the Govt/RBI FIRST.
Again at the cost of repetation on your query no.2,i would say that there is no restriction while Indian Promoters help or facilitate or act as promoters and incorporate the comapny for non-residents ,by doing this you can perhaps save the time and you are not required to take signature on all the incorporations docuemnts from outside India.This is the benifit.The transfer of the share of the proposed company can be done at the later stage through the Form FC-TRS provided you have to check that the non-residents investment of fund qualifies for automatic route under FDI scheme .
Regards