Is this permissible?

I choose to invest in the areas where it is permissible.  

They’ve repainted all the blonde wood kitchen cabinets with Cherry wood stain (not well done), they’ve opened a bathroom wall party and inset shelving 3ft by 8 ft, they erected a large canopy in the back yard and built an attached tool shed (both not permitted) and so many other similar things.They had never asked permission of me to perform any of these changes and I am wondering how I go about collecting on repairs that will far exceed their original security deposit.

Now you have his permission to tell him so do it.    

Generally, short sales will have deed restrictions that prohibit you from reselling for somewhere between 30-60 days, unless you get permission from the lender prior to closing.

The city official said that he was not giving me permission to have an airbnb but that there were only 4 city zoning employees and that it was very unlikely that I would ever be caught.

If that's the situation, the lender will have to approve the sale and they will want an agent to list the house and handle the shortsale process.If it does have equity, you will have to work up a deal with the owner and the owner will need to get permission from the bankruptcy trustee to conduct the sale.

When I reviewed the short term rental regulations page on denvergov.org I see they have a stipulation that "Written permission must be obtained from landlords or owners".

Got two wire sticking out of the ceilings in each room, all four rooms.Now, I gave tenants permission to install ceiling fans.

Another change was to the electrical install for in floor heating has to be done differently than last year.The good news is the semi-d project received all of its permission to proceed.