How sound are the popular comprehensive formulae of seeking forgiveness, and do they contain any doubts?

Seeking forgiveness (Istighfar) is asking Allah for forgiveness. It is permissible in any form that does not involve a Shariah violation. The forms mentioned in the question are permissible as long as no particular specificity is believed about them or they are not made a habit restricted to a specific time. The Prophet, peace and blessings be upon him, taught us the master of seeking forgiveness (Sayyid al-Istighfar): "O Allah, You are my Lord, there is no deity except You. You created me, and I am Your servant. I am abiding by Your covenant and Your promise as much as I can. I seek refuge in You from the evil of what I have done. I acknowledge Your blessing upon me, and I acknowledge my sin, so forgive me, for indeed, none forgives sins except You." Whoever says it with certainty and dies on that day or night will be among the people of Paradise. The master of seeking forgiveness fulfills its conditions when it combines sincere intention and truthfulness with Allah.