There is no tashahhud after Sujud as-Sahw because the Messenger of Allah (peace and blessings of Allah be upon him) did not do that, as is indicated by the sahih hadiths.

If you forgot to do sujud as-sahw, you can make it up if you are still in the mosque and a long time has not passed. If a long time has passed or you broke your wudu or you left the mosque, you do not need to do the sujud and your prayer is still valid.

What is to be said in Sujud As-Sahw is the same as what is to be said in the sujud of prayer, which is to say Subhana Rabbi al-A’la or other tasbihat which are reported as being sunnah to say in sujud.

If you are not sure if you prayed three or four rak`ahs, you should consider the most likely case. If you cannot put more weight to one of the two, you should assume what you are certain of and that is the lesser amount, and make sujud al-sahw.

This is how to stay focused in prayer: 1- Seek refuge with Allah from Satan, 2- Blow with mist to the left three times.