Since being away from the technology, what are some of the best practices of today? Backend, front end. php, asp, off the shelf dev tools?

Parse is indeed one of the best for user accounts, IAP tracking, custom push, analytics and user data sets. You can watch this video http://www.youtube.com/watch?v=E_0llIdtYNA on Youtube for some basic understanding of the Parse platform.

If I was just starting out, I'd consider learning Meteor (https://www.meteor.com/). It's just entered version 1.0 and after working with it for a little less than a year I do have some issues with it but it still makes for a very solid framework that gets you up and running very fast. You would only need to learn Javascript, and you can slowly work your way towards nodejs from there (which Meteor is based on) if you want to, or you could get the basics down and focus on learning design if you prefer.

Yes Wix supports a mulitude of APIs to used for various fetch calls for your web pages. If you already have to API's in mind you can venture off within you WIX code to integrate within your application's processes. There shouldn't be any complications getting this done. Please see the link below for more information https://www.wix.com/code/home/api

I hope this answer will help you in two ways: It should help avoid unnecessary expense being incurred and it should also help you recruit software engineers to build your project. Before you spend a single dime on building, I'd encourage you to validate the idea itself with potential customers. Identify the kind of person you are thinking of solving a problem for, and just explain the high-level concept. Make sure that a sufficient percentage of them are saying "yes, I need this." Then, really distill the idea further into a single piece of functionality that this customer base says they want. There are tools that allow for "drag & drop prototyping" like fluid.io that you can use to create a clickable walkthrough of the user flow you're looking to create. The more that you can do to validate the idea and focus it, the more you can define your "Minimum Viable Product." If you can't find enough of your potential customers to get excited about the idea, I would advise against hiring anyone to implement anything. That said, it's also a lot easier to recruit talent when you can say "I spoke to 100 potential customers and 40 of them said they would use this" or better yet, pay for it. Convincing anyone to work on your idea will be considerably easier if you can show some existing proof or interest around the idea. From there, your best source (assuming you don't have a network of people to draw from) might be local colleges & universities. I would advise against hiring online or working virtually with someone when you are new to building product. I'd be happy to talk to you about your project, how to validate the concept and how - if you decide to pursue it - to hire good talent. Best of luck!

https://www.filepicker.io/ is the best thing that you can integrate with this app which suits your requirement. If you are the owner of the app, you can integrate it very quickly. If not, you can suggest the app owner to do it Feel free to call me if you need more clarification. I am consulting architect for few companies in US and India on mobile, web and windows/linux/mac apps.