what happens after i harvest all my plants ?

Meaning, lets say i cure/dry the buds etc and take out all the leafs to make hash, can i use the naked plant to grow some more weed ? Do i just wait another 3-4 weeks for it to grow back and then i can flower again?

Yea its called re-vegging....But you need to have actual leaf and/or buds on the plant in order to do that.

If its completely bare (just bare stems) then nothing will really grow on it.

im fairly sure you can do this, but the buds next time round wont be too great the plant is old regardless.

if youve got no more seeds, a slightly better option would be to take a clone and put it into veg.
seriously not ideal at that stage of flowering though...