I Got Shortlisted For A Federal Civil Service Job

 I'm posting this here in order to get more clarifications regarding this recruitment exercise by the federal government of Nigeria.

So, sometime in March, I applied for same job when it was announced. I applied and I prayed for success. Just four days ago, a friend whom we applied same day, called to inform me that the lists of shortlisted candidates have been released and that I should check the Portal. But before I checked, I asked about his own status and he said he wasn't Shortlisted. When he said this, I instantly lost hope. I told him there was no point checking it because I already knew I would not be shortlisted too, so what's the point checking?. He insisted that I check. I was nervous.

To my surprise, I finally checked and saw that I was shortlisted. And I can only pray that I succeed after all. To God be the glory.

For those who are already in the system, how are these things done?.

Secondly, I heard exams/aptitude test would be next, but no date has been fixed yet. Does anyone know the Exact date?

Thirdly, what and what do I need to study ahead of the test?. What are the kind of questions involved? I was told it's Mathematics, English and current affairs. How true is this?

Lastly, how much is the salary for starters when you get a federal civil service job. I can see Grade Level 8 on the dashboard. Does this mean that if I succeed(by God's grace), I would start from level 8?