Some of your questions (2 & 4) should be answered by doing proper research. Start learning the Qt Sdk from the official site.

About 1) Its VERY subjective.

Some prefer C++ because you have less dependencies. You only need to include Qt to have everything.
Some prefer Python, because you dont have to worry for memory management.

At last, you need to try both.

About 3) That's a strange question: What do you mean about "easiest to port"? You can only "port" an app, when you have the source code.

When you are unrelated to the apps, you need to rewrite everything from scratch, so every application has the same insane difficulty.

In the case of Blackberry Messaging, you also need to understand the messaging protocol, so you will have some reverse engineering work. AFAIK, no one has been succesful with this.

Hope this helps