1. Can a girl speak to the chosen boy if they desire to get married.
2. What is the extent they can speak with each other while beig a namehram to each other.
3. In a situation where clarity/clarifiations are required before wedding, can they speak.
4. Also if it is not flirting, can such convrsation be made?

As long as the intention is to get married to the person, then you can discuss issues relating to your future etc.
Best way is to give a contract of Mutah recited with parents aporoval so you can discuss things more fluidly.