HAML vs Swift

Hello, I am still a student and would like to ask a question. Currently, I am developing in mobile development with Flutter in the frontend and Python in the backend part. Right now I have to make a choice about developing a mobile app or developing a backend to progress more professionally. My questions are as follows:

1. If I prefer the mobile application area, will I only work with the Ui/Ux developer with the front-end and code the designs in Swift Kotlin languages, am I responsible for the back-end software?

2. I have a product that generates new ideas so I like to control the development and work there because the backend is the brain, but are they independent from each other in the backend mobile application? Is the mobile app developer responsible for the backend software?

3. I don't like graphic design because I don't like it if it's not perfect and I get stressed. Am I responsible for the graphic design in the mobile app?

4. Is a mobile app developer also a backend developer?

I know these are very simple questions, but they are very important to me. Thanks for your answers.

As a startup, we need the maximum flexibility and the ability to reach our customers in a more suitable way. So a hybrid application approach is the best because it allows you to develop a cross-platform application in a unique codebase. The choice behind Ionic is Angular, I think that angular is the best framework to develop a complex application that needs a lot of service interaction, its modularity forces you (the developer) to write the code in the correct way, so it can be maintainable and reusable.

Hey there, we are looking to develop our own layer 1 blockchain. We're splitting the responsibilities for origination, clearing, and settlement across three independent but cooperating node networks. We've gotten our Proof of Concept up using Ruby on Rails for the nodes, you can see it as the attached link. So far, so good. Now we are looking to convert it into a distributable and are trying to figure out which language is the best for this.

Essentially our needs from the language are: solid networking tools and speed, very fast execution of basic actions, some parallel execution, and able to compile the end product into an easy to distribute and use package for end users.

I was learning Rust, but I have a healthy amount of experience with Swift and right now, it's only me coding. I've only done iOS coding, but have built a fintech app from scratch that's now in the app store so I'm pretty familiar with the language and its benefits. Haven't experimented with Vapor or any of the application development tools, and I wanted to know if it is a crazy idea to develop a blockchain node in Swift instead.