Welcome, and thank you for the kind words. 
As @pantheon mentioned, There are many different members here who will be able to help you on many different topics. I myself just happen to stand out because I am interested in two things which most people find very boring. 
First, I was a network engineer, so I know a lot about the communications protocols and tend to keep up on the most recent news. Most people don’t need to know much about that , so I tend to be one of only a few who post in those threads.
Second, I’m a hardware guy. When a new device comes out, the first thing I do is read the testing lab reports and the second thing I do is read the user manual. And only then do I start looking at the marketing materials and the glitzy new “smoke and mirrors” marketing video of the company has released. 
It’s like being a Game of Thrones fan whose primary interest is costume design. You just pay attention to different things. (By the way, did you know that some of the winter scenes were filmed in a warm climate? so to keep the actors from fainting from heat exhaustion the fur cloaks had tiny tubes sewn in and a cooling unit that pumps ice water through them.)
Let’s see, where was I? LOL!
Anyway, I don’t answer anything about code (I depend on text to speech software and, trust me, you don’t want to try to do groovy coding with text to speech.) I don’t talk about wiring beyond the specifications of the device you’re considering wiring in. I stay out of most of the discussions these days about the apps because neither one is voice navigable and I’m getting really out of touch on those.
But device specifications and in particular comparing one candidate device to another for a particular use case is the part I really enjoy, and the part most people don’t, so that’s where you will tend to see me the most. And where I tend to run into new folk in the community. 
But I digress. 
Most of what you’ve described can be done with the classic app. But because of some changes in Samsung’s design philosophy, some of it, like the door unlocking, cannot be done with the new app, and that may be an issue since we’ve been told the classic app will be going away eventually, we just don’t know exactly when.
And some of it, like shuffling to Spotify list, depends on features provided by the third-party integration, in this case echo, which I’m not sure are available. You can definitely have echo start playing a specific station. But I don’t know if that’s enough for what you want.
Before we go any further
The first rule of home automation:
The model number matters.
We need to know the brand and model of the smart bulbs and the sensors and even The smartthings hub. We even need to know which country you are in. And which version of the SmartThings mobile app you are using.
Then we can start looking at the individual use cases.
Welcome again! Sounds like a very cool project.