Can I shave today for kvod Shabbat, because you can’t shave on Rosh Chodesh?

Do I need to repeat the amida if I don’t remember if I said המלך הקדוש?

If someone forgot to do Al hannisim does he need to repeat shemone esre

I forgot yalah veyavo by shacris (rosh chodesh) what sld I do now?

If I missed mincha, I daven arvit twice, but do I add Yale viyavo in both amidahs if it’s rosh Cho de ?