How it is better to organize processing of different types of data from the form on the server?

Question

JavaScript

Hello! I am writing an application for my work to make life easier for myself and my colleagues. The essence of the application is the creation of an application, with the subsequent addition of information on this application and the formation of a response.
Created many large forms with different INPUT types. Then it was divided into phased (step-by-step form) filling. In these forms, you need to provide for uploading photos and editing them. It will mainly be used on mobile devices. I want it to be similar to the FACEBOOK EVENTS application.
1. What is the best way to organize data loading?
2. Split into separate requests to the server, or when adding a photo, wait for the download and continue filling?
3. What are the best plugins to use for uploading files and editing photos on the client?
4. The use of Input with the Hidden type is currently relevant or in 2017. Is there a better way to save information between intermediate stages of communication with the server?
5. Where can I find examples (Git) of organizing processing (patterns) of different types of forms, validation of complex forms on the server?

Answer 1

1. What is the best way to organize data loading?

Well, either through a post-request, or in some cases I load via web sockets, depending on how it is more convenient in this case.
If it suits your implementation, then it is relevant)