1)    When praying the supplementary prayer, the person must pray according to the applicable laws of time of the new prayer, and not of the previous (missed) prayer. For example, one who missed the afternoon services on Friday, prays two evening Shabbos prayers on the evening of Shabbos. If he erred and prayed the supplementary prayer in the form of the prayer that he missed and not of the prayer that he is up to now (e.g. he prayed a weekday Amidah for the supplement on Friday night), he has fulfilled his duty. (Shulchan Aruch and Mishne Berurah 108)

2)    If on the evening of the new month he forgot to pray the evening service and prayed the morning service twice and in the second rendition of the morning service he forgot to say “Ya’aleh veyavo” he does not need to repeat again as if he would have missed it out in the evening service he would not have had to repeat it. Similarly, if there were two days of the celebration of the new month (Rosh Chodesh) and on the first day he forgot to pray the afternoon service and therefore replaced it by praying the evening service twice, even if he forgot “Ya’aleh veyavo” in the supplementary prayer he does not need to repeat it, as in the evening service of the new month, one does not repeat when it has been forgotten. (ibid)