Inconvenient Document Template Access Issues and Send To connections in SharePoint

What?

You have a SharePoint site (Site A) that has got a content type with a document template attached to it.
You have created a few documents using the document template and them moved them into a different site (Site B).

A user who has access to the document in the new location (Site B) but does not have access to Site A tries to access it and gets prompted to authenticate against Site A.

Eventually being a not so technical end user, he gets his accounts locked after trying his credentials repeatedly.

How to reuse / associate list workflows built using SharePoint Designer 2013 on multiple lists

What?

How to reuse / associate list workflows built using SharePoint Designer 2013 on different lists

Why?

You want to built a reusable list workflow using SharePoint Designer 2013 and be able to attach them to multiple lists.

You receive an error "The {Send To Connection} site could not be found or accessed." when you try to send a document using "Send To" in SharePoint 2013

What?

You receive an error "The {Send To Connection} site could not be found or accessed." when you try to send a document using "Send To" connections in SharePoint 2013.

Why?

I have tried to copy documents from one site collection (Site A) to another (Site B) using Send To connections in SharePoint 2013. Documents sent from Site A to Site B were sent successfully whereas documents that are sent from Site B to Site A failed with the exception: "The {Send To Connection} site could not be found or accessed."

How to fix SharePoint 2013 Designer list workflows on pages libraries that automatically get cancelled with HTTP 500 exception

What?

List workflows that are built using SharePoint 2013 Designer on pages libraries in SharePoint 2013 get cancelled automatically with internal status "Cancelled" as shown below: