incorrect recitation

Incorrect recitation

Q: I realized that I was reading surah Ikhlas pausing in letter Mim (everywhere where it has sukun in this surah) in last ayats making it as double letter – shadda. Does it change the meaning? If during salah I realize I did it again, do I have to start salahs from the beginning or I have to make sajda-sawh or can proceed without it as normal? Could you please also let me know, is it true that kaza of sunna of fajr cant be made in a fajr time, but has to be made any other time after fajr?