From my very basic understanding of what transpired, the hotel security were trespassing by entering a rented room. I'm not altogether familiar with state law in Nevada, but that could certainly be argued in California.
Exactly. Cops can't break into a hotel room without a warrant, but agents of the management might be able to, depending on local laws. The 4A doesn't apply to them.
That's because the 14th Amendment extends the "due process" requirement to the states, and under the [Incorporation Doctrine](https://www.law.cornell.edu/wex/incorporation_doctrine) respecting the 4th Amendment has been considered part of "due process".