Two questions

1. Why are the skills that the characters is "given" as starter skills also included in the first rank of their class, sometimes at a high cost, the character will already have these skills and thus cant buy them again since they should be buying the +10 version of them in the next rank.

I've checked Dark Heresy and it doesnt relist the skills, is this just a quirk of the fact the characters are already at 4500 xp ?

2. Trained Basic Skills

I assume a trained basic skill means, you treat the skill as basic rather than advanced AND treated it as trained, so you roll using full value of the attribute.

I assume this differs from any entry (yet to find one) that says "you treat .... as a basic skill" (but doesnt mention trained)

If desired, you can use a Rank 1 RT career as a Rank 5 DH career. In such a case, you would gain the ability to purchase those skills, and would need to do so if you want to fulfill the functions of the career. This doesn't really apply to Astropaths and Navigators, but most others can be adapted pretty easily.

There's also the idea that some of the Skills/Talents can be swapped out with GM permission, and this gives equivalent costs. An example I've seen is allowing a Missionary to swap out the starting Basic Weapon Training (Universal) for Flame Weapon Training (Universal), and other situations may come up too.