For accuracy fiducials must be on a copper layer to ensure alignment between the fiducials and the pads that are also on that copper layer. Fiducials on a silkscreen layer would be useless, as would fiducials on an inner copper layer. If you do not have any smd components on the top layer then there is no need for fiducials on the top layer. If you have smd components on the bottom layer then you need fiducials on the bottom layer, otherwise fiducials on the bottom layer serve no purpose.
This is something you can discuss with your fab and should be inline with the requirements of the equipment that will be assembling the boards. But all of these surface treatments are acceptable according to IPC7351.
There is obviously no need for solder paste. See above regarding both sides of the board.
An even number would be fine so long as the pattern is not reversible. Three global fiducials, spaced as far apart as possible, are usually preferred. The grid is irrelevant.
There are global and local fiducials, you should be aware of how and when to use both.
So where lies the source of your confusion?