Despres Photography

We have an assignment and i need to achieve this.

a) 6 feet from the subject with small aperture/opening (maybe around 22-29)

i must only focus each of the ff: foreground, middle ground and background
and the last shot i must focus all of the above

b) 6 feet from the subject with big aperture/opening (maybe 5.6 and below)

i must only focus each of the ff: foreground, middle ground and background
and the last shot i must focus all of the above

so for each A and B, i must have 4 shots each. a total of 8 shots.

assignment C and D are the same like above except that the distance from the subject must be 3 feet

my question now is, Is it possible to focus all ( foreground, middle ground and background) with big aperture at a distance of 6 feet and 3 feet? or you can only focus one thing at time?

my DSLR is canon 350D with a 18-55mm lens.

i hope you can help me. thanks.