No commercial or industrial activities at all are allowed. This suggests an intent to shape a district of purely residential character and gives a possible basis for denying a commercial use. The zoning checks out and a permit can be issued consistent with the zoning ordinance. The answers depend entirely on the local ordinances. The local ordinances have to say in what order permits are issued and whether one permit can be held up until another permit is issued, and whether one permit is conditional on issuance of another permit.
Many ordinances exempt minor improvements and farm buildings.
The use still has to comply with the use and dimensional rules even if there is no need to take out a permit. This is set by local ordinance. If the ordinance does not say anything, the general rule is that the permit is good for as long as the ordinance remains unchanged as to the intended project. If the ordinance changes and the project has not begun or is not so far along that it is nearly impossible to change, the applicant should reapply for a new or amended permit reflecting the new rules that apply to the project.