Mateen Charbonneau

There is a very beneficial video series about the topic here:

https://youtube.com/playlist?list=PLD2F0DFA18BFBD747

If the person has agreed to this in their lifetime  then it is allowed.

A Kaafir is someone who is ungrateful. This term is used for disbelievers because of all of the things Allah has given them they are ungrateful to Him and deny Him.

It is allowed to kill insects posing harm to us. 

Pure would be permissible for us to use and ritually pure. 

We can enjoy the permissible worldy pleasures while staying in the boundaries of Islam. 

He had the choice to sin or not. Some beings are stubborn and arrogant. We see this with humans as well that they know the truth of Allahs punishment yet still persist in sin knowingly. 

Yes he is a prophet. 

Yes a woman can swim if she is wearing the proper islamic covering. A lot of times the women swim in a place for women only. 

We should ask for Allah's help in our endeavors  

You should not abandon hope for her. Continue to encourage her, while not being forceful or pushy. Pray where she sees you and perhaps she will feel remorse that she is not praying. 

A scholar in Najaf told me about being persistent, "I remember there was one of the youth who followed my father in taqlid and at some point he became a communist and left Islam. My father would pass by this youths shop on his way to salat everyday. My father would always say salam to the youth, but the young man would ignore him and never reply. My father kept saying salam to him everyday for one year then the youth finally replied to his salam and ended up repenting and coming back to Islam."

In the book Aqaed al-Haqqa by Ayatullah Sayed Ali Sadr we find infallibility categorized into 3 levels:

1. Ismat ul Kubra which is reserved for the 14 Infallibles. They do not commit sins, mistakes or even tark al-awla (choosing the less preferred method). We as Shia however do not believe that any of the prophets, from their birth until their death, committed any sins at all whether big or small. We see that the honorable Shia scholar, Sheikh Mufid stated that the prophets and Imams never committed sins or even left the recommended actions (mustahab) and that they were perfect in every aspect of their lives.

Another point to bring is that the prophets are not infallible by force. Rather, they are infallible by utilizing their intellectual ability to not succumb to sin. They have the ability to sin, but they choose not to sin. They know the effects and evil disgusting nature of sin and are repulsed by it. An example would be, if we saw an old piece of food that was rotten would we eat that food? Of course not! It is repulsive to us because we see its rottenness. This is how the prophets see sin. They see the rottenness in disobeying God, whereas most of mankind is attracted to the sins because they have been made fair-seeming to them.

2. Ismat ul-Ithbaatiya which is for the general prophets where they do not commit sins, but it is possible for them to do tark al-awla (choosing the less preferred method).

3. Ismat ul- Thubutiya which is an acquired level of infallibility by abandoning sins and continuously doing their responsibilities to Allah and are obedient to Him. They are just individuals and are far away from deviation. We find this type of acquired infallibility in some of the progeny of the infallibles such as Zaynab, Abbas and Masuma (as) and others.