Do we have to obey the parents in every condition or they say or put on us, what if it is something that is continuos forever until you die, such as: always offer the sunnah prayers for every prayer, do we have to do this even after we have become adults in the sense of islam (baaligh) or even after they have passed away? And if you can Please support your answer with logically applicable hadiths on this question and the parent's right from Quran and sunnah, and stories of the companions etc.
There are many Ayat & Hadith about parents. I will start with the famous one.
وَقَضَى رَبُّكَ أَلاَّ تَعْبُدُواْ إِلاَّ إِيَّاهُ وَبِالْوَالِدَيْنِ إِحْسَانًا إِمَّا يَبْلُغَنَّ عِندَكَ الْكِبَرَ أَحَدُهُمَا أَوْ كِلاَهُمَا فَلاَ تَقُل لَّهُمَا أُفٍّ وَلاَ تَنْهَرْهُمَا وَقُل لَّهُمَا قَوْلاً كَرِيمًا
And your Lord has commanded that you shall not serve (any) but Him, and do good to your parents. If either or both of them reach old age with you, say not to them (so much as) “ugh” nor chide them, but (always) speak to them reverent speech. Surah Al – Isra’, 17:23
Narrated Abdullah bin Amr: A man said to the Prophet, “Shall I participate in Jihad?” The Prophet (peace be upon him) said, “Are your parents living?” The man said, “Yes.” The Prophet (peace be upon him) said, “Do Jihad for their benefit.” Sahih Al-Bukhari – Book 73 Hadith 3
So In the light of this Ayah & Hadith You must respect, take care and obey your parents. Now according to your Question: Do we have to obey the parents in every condition or they say or put on us?
The Answer is NO in only condition if your parents forcing you to do shirk or pray for other God Except Allah.
The Other Question of yours is: such as: always offer the sunnah prayers for every prayer, do we have to do this even after we have become adults in the sense of islam (baaligh) or even after they have passed away?
I must say that its a question which contain answer of someone opinions. I Will answer it with question. If your parents says that do take care of your health then what you will do even after they passed away? off course you will take care of your health because you know that its right and good thing for your life. Similarly pray sunnah is a good thing for you and for us because we all need to do good things as much as we can if we want to go to jannah. but if you will take this thing with your head that your parents also used to say this that "Offer sunnah" and its right. then go for it. You will get the ajar for Both Sides. 1 for Sunnah &1 for Obeying your parents. Hope this helps.