Recording one's Salaah due to frequent doubts

Q: If one has frequently doubts in salaah, that he is recording his salaah with his audio-record function of his phone to check afterwards whether he prayed correctly if some doubt arise about something. Now say he is praying Zuhr and in the last rakaat when he sits after the sajdah, he does not not know whether this was from the 1st sajdah or 2nd sajdah i.e. he cannot totally remember that he did another sajdah before it, but continues on this basis (because he can check with the audio-record anyway) and finishes his prayer. Now afterwards when he checks his audio-record it shows that he did 2 sajdahs thus prayed correctly. Is the salaah valid ?

Last time of Maghrib Salaah

Q: If one is for example about to pray Maghrib after the time of those who calculate end of maghrib time with 12 degree or 15 degree, but one is still before the time of 18 degree, should one make the intention for the adh'aa of that days Maghrib or for the qadh'aa of that days Maghrib ? For example Maghrib time is at 20:00 according to 12 degree Maghrib ends 21:15, according to 15 degree, it ends 21:40 and according to 18 degree it ends at 22:00. Now how must I make the intention if I would start praying Maghrib at 21:25 or at 21:45? Because when I am in such situation because of the waswas of what to do, I pray one time as adh'aa and after it repeat one time as qadh'aa. Should I make intention to pray the current day Maghrib, or the currents day qadh'aa of Maghrib in such a case? Or can I make intention like ''I want to pray the Fard of Maghrib of this day, which I have not prayed yet'' does such intention then count for both i.e. if it was a adh'aa it will count for adh'aa, and if it was a qadh'aa it will count for a qadh'aa? Does such an intention count according to Abu Hanifa, Imaam Muhammad, Abu Yusuf? Should I avoid that during my salaah in the above case of Maghrib that the specific time of 12 and 15 degrees falls in the middle of my salaah, since according to Abu Hanifa entering a new time during salaah would make the prayer faasid?

Refraining from areas of doubt

Q: I loved a girl. We both were in love for sometime and family come to know about us. My family accepted our relationship and my mom asked there daughter for the marriage for which they refused. We are not in touch after that. After one year they sent us the proposal that they want to marry this girl to me. But I come to know some strange facts that she also had a relationship with her uncles and she also has boy friends. I didn't know she was a cheat. I have all the proof that she used to talk with her cousin brother and uncles over the phone. Please advice me. Is it permissible to marry this kind of girl?