Need advice on an Internal Full-fledged Application Request Tracking System Flow Design, with prepopulate template, restricted achieve, multiple attachment, status update, etc

[Hairong_zhu]

Dear Community, 
I don't have any IT coding background and have been designing an internal payment application process flow system for my finance department.  Our company has all the Microsoft Applications available for my design use.  (SharePoint, TEAMS, Power Automate, Forms, etc.)
Company internal users would use the flow for applying payments, who have corporate Microsoft accounts to use all the MS applications. The general process flow system design sequence and requirements would be as follows:

Flow Requirments:

1. An applicant user would fill up a payment application form designed by me with some information fields, option fields, mandatory fields, and multiple attachments that are required for submission.
2. The form can be filled by the user manually, or using a prefilled template to minimize the manual filling effort for past revolving applications.
3. Upon submission, the form will be sent to 2 approvers in designed sequences.
4. Upon a form is approved or rejected, an email and TEAMS message will be sent to the respective parties for notification.
5. The form needs to carry the following features:
   1. It can show the process status by all users (e.g. New/Submitted/1st approved/ 2nd approved/Rejected, etc )
   2. It can not be amended after submission by any users, unless only if it is rejected.
   3. It will be achieved together with all the attachments it carries, with only view access allowed to all users in the end.

Problems that I encountered so far:

1. I am not sure which application should I use to design and host the form.  Both the Microsoft Form application and the SharePoint List don't have a prefill template function.  I thought about designing a separate SharePoint list just to store the templates so the user can copy the template list item to the actual list item, but it doesn't seem to be a very smart way of doing things due to large groups of potential users.  If all of them use one SharePoint list to store everyone's templates, it will be a mess.
2. Archiving is also a big problem with attachments.  At first, I want to create a 2nd SharePoint list and copy everything over after an application is approved.  However, the system won't allow the attachment to be copied over because it requires the applicant user to have an amendment entitlement to the achieve list, which defeats the purpose of limiting archive access to view-only for all users in the first place.
3. Another problem is to not allow anyone to amend the form after it is submitted unless it is rejected.  In a SharePoint list, though I can carry all the list item information until it is achieved, I found that I can still amend the attachment after submission.

It would be greatly appreciated if anyone here could give me some guidance, ideas, or advice.

Thank you.

[RobElliott · Accepted solution]

@Hairong_zhu you've not mentioned Power Apps which is what I use in conjunction with SharePoint lists and Power Automate when I am asked to build something complex like this. It has the advantage of being able to use multiple data sources in the same app so you could probably have a list for the templates and separate list for the applications and archive. Another advantage to using Power Apps is that the user is not directly seeing the lists but their interface is pourely with the app. So I recommend you investigate Power Apps; there are plenty of very good videos on YouTube to get you started, particularly those by Shane Young, Reza Dorrani and April Dunnam.

Rob
Los Gallardos
Intranet, SharePoint and Power Platform Manager (and classic 1967 Morris Traveller driver)