InfoPath Dev

 So glad to hear that you have it working. It can be difficult, sometimes it takes a second set of eyes that are familiar with the system to see things that we don't because we've been staring at it for days on end. :)

 So glad to hear it! Believe me, I've been there before. I'm just happy I can help! =)

From the looks of it, every headache you are getting is due to the check-in/check-out implementation. Humor me. Create another copy of the form, (make sure you edit the Data Connections and Publish it to a different Library so you don't overwrite your existing stuff, dump the check-in/out, and simply hide or disable fields based on the view or ...

 Ok, a web service warning is typically a connection issue. I get it a lot when I use User Profile data connections here at work. It's intermittent, so tough to track down sometimes. That said, the Log ID and Correlation ID should tell you exactly what the issue is, if you have admin rights on the server. I have local admin rights, ...

 Go into the library. Click on the Library Tab at the top. Click on Library Settings. All the way at the bottom, there will be views, click on the one that says "All Views."  The next page should give you all the columns that are available from your form. Click on the TestDDL column and choose the number where you ...

 No, she means Checked_Out_To is not blank. Because the rule is running upon the form being opened (Form Load), you want to make sure you're getting a form that isn't already checked out to another user.  

 I would suggest doing the heavy lifting on the form itself, or use a simple approval process that has it set in series, whereby it'd go to each department or specified persons in the order you select before the form becomes "live and editable." The other option would to create rules that hide or disable field from ...

 To add to what Hilary stated: Using formatting rules to hide/show sections leaves less overhead, and it's less moving parts for you to think about/deal with. I had an order request form created that had a different view for each vendor (Staples, internal ordering, etc.) and it was just a huge headache. All told it was ...

 Unless everyone has InfoPath form filler available to them, you'll have to use a web-based form. I prefer it myself. Here's a good video on this, and I HIGHLY recommend her book, as Chapter 11 walks you through step-by-step. https://wonderlaura.com/2012/05/16/creating-a-workflow-initiation-form-for-approvals/  

 Hi zakaria.botros - If you're looking to do an actual form (like request for time off, or supplies, etc.), then check-in and check-out probably isn't going to be the best option. Forms are pretty much used to compile data to a list or library from multiple users. You might be better off just creating a file (Word, Excel, ...