In regard to 1
Owners are free to rent there parking space to anyone. However there may be a by law restricting who they can rent to.
In the case of an exclusive use by law, the by law only permits the owner the use of the car space. This is different to the case where the lot owns the car space. In an exclusive use bylaw the ownership of the car space remains with the OC and hence it controls how it is used
In regard to 3
The affected lot owners would need to have their exclusive use cancelled. The lot owners need to agree this in writing before a motion is taken. Then a new exclusive use bylaw is raised showing the swapped car spaces.
The old by-law needs to be removed and the new by-laws registered on the strata title.