The incubation process means a rest of no intellectual activity at all or after photoreading a book can I do something like study other book, do exercises of other subjects, activate other book ,play the guitar, etc (any intellectual activity)?

Incubation means getting away from the material you've just photo read. Yes, you can do whatever else.

Incubation is the period between photo reading and manual activation of a particular text.

Thanks a lot for your answer!