To create Wordpress based applications:
Here a list of frameworks and starter temes: https://includewp.com/
Here, one than promisses the moon: https://piklist.com/
Here, one that is not on the list: https://wp-papi.github.io/
Here, one that seems to be very handy: https://github.com/hiwelo/raccoon-plugin/wiki/Manifest-features
A helpful online tool for wordpress development:
The easiest and the fastest way to create custom and high quality code for your WordPress project using the latest WordPress coding standards and API’s.