Answers:
#1 depending on how hard the rain fall is and how soon after the last trawl the rain could be beneficial to the curing process by keeping the concrete hydrated.
#2 Minimum of 24 hours before the equipment is set and secured to the concrete, if you are going to have expansion joints cut into the concrete you also wait 24 hours and it will have to be done with a concrete saw blade because of the hardness in just 24 hours.
#3 yes, equipment and electrical
#4 Typically gaps are filled with hydraulic cement
#5 the shell needs to be washed and vacuumed out prior to the installation of plaster, the plaster crews will do this if it’s a small amount but if theirs lots of debris they sometimes charge for their time.