Before nikah, you are a non-mahram for her. so the same rules of non-mahram applies to you. you cannot look at her picture.
The only condition for you to look at her picture anytime, is, when you do nikah with her, otherwise never.
Regarding talking to her, before nikah, you can talk to her once or twice, but only in presence of her parents or wali. it is better not to visit her multiple time or talk to her too much.
You follow a western concept that you MUST know your wife, befoer marriage. this concept is not islamic. in islam, you dont know if she is good or bad for you. You just have to marry her, withotu knowing her, because its Allah, who knows better than you, that if she is better for you or not. If you want to take guidance from Allah, then do istakhara before engagment (or giving her your word that you will marry her). Once you do, then dont turn back. Because the more you will know her, their are more chances that you will fall in love with her and you might like/dislike many of her habits (which is natutral), for which you can change your decision. so stay away from this evil concept of KNOWING girl before marriage properly. and put your trust in Allah. In sha Allah, Allah will do the best for both of you.
And Allah knows the best.