Using ConnectApi we can filter filter PendingReview Feeds by using :
getFeedElementsFromFeed(communityId, ConnectApi.FeedType.PendingReview, pageParam, pageSize, ConnectApi.FeedSortOrder.CreatedDateAsc);
There is also a provision to filter feed by user/group :
searchFeedElementsInFeed(communityId,feedType,subjectId,q)
But I couldn't find any method/provision to combine both and get FeedType of PendingReview for particular group