Dawat and Tabligh

Doing Deeni work under the supervision of someone who is well grounded in Deen

Q: According to the Hadith "al Quranu hujjatun laka au alaika". If I go from place to place reminding my brothers and my self regarding Deeni tenets, will this ayat alone somehow be sufficient for my immediate salvation? Or will I be given the ability to fully act according to Deen by Barkat of this or any other ayat with steadfastness?

I am afraid you are going to answer that if I do not act on the remaining verses but stick to one Quranic verse, the bad will out weigh the good and the Quran will be proof against me.

Giving dawah to non-mahrams

Q: I am a teen at the age of 17 and I am wondering if it is permissible for me to give Dawah to a non-mahram female. So I can keep in contact and choose her for marriage when Im ready. As of now I have made no absolute contact with her or exchange of words. 

Were the previous ummats commanded to invite towards good and forbid from evil?

Q: Kindly clarify whether it is correct to say that in the previous ummats, only the Nabi was allowed to give dawat. As proof, it is said that Hazrat Haroon (Alayhis Salaam) was made a Nabi in order to accompany Nabi Musa (Alayhis Salaam). But is it not the case that the person mentioned in Surah Yaseen also gave dawat to people by asking them to follow the Nabi? Also, people in previous ummats had to act to prevent people from wrongdoing (preventing evil is also considered part of dawat). Does this not show that ummatis of the previous ummats also had to engage in some form of dawat?

Missing one's wife while out in jamaat

Q: I'm far away from my wife and can not manage to go see her as I am in jamaat, looked at her photo in phone while in toilet, and suddenly I could not control myself, the semen came out, I don't know what are the steps forward. As I know it's a sin but I was very desperately in need. And I'm in a 3 chilla, and it's getting quite difficult for me, as it's only my first chilla.