ismaili/aga khani

I have a few questions.

  1. do you guys pray the same way as other muslims? like five times daily following the same procedure with minor difference?
  2. Are others allowed to visit the jamaat khaana when you guys are praying or during other times.
  3. I had a friend in high school who was ismaili and remember him telling me that the next imam is the eldest son of the current imam. Now I read in the other thread that the current imam chooses the next imam. Which is it?
  4. If the current imam chooses, then does he leave a will or does he declare it during his lifetime?
  5. What if the imam doesn't have any sons?

Thanks