Hi Vinu,
In response to your first query I wish to inform you that, so far, there are no provisions or precedent which bars filing of application for RCR when Dv maintenance case appeal is pending, therefore the RCR can be filed.
Further in response to your second query I would like to inform you that it will certainly have impact on the interim maintenance granted to her as in the case of RCR husband maintains his wife and children as a matter of responsibility and not as a liability arising out of some legal proceeding.
Further RCR restitutes the conjugal rights of both the spouse and thus, practically, the order granting maintenance cannot be adhered to.