Salesforce Integration | APPSeCONNECT

Salesforce Integration

In which components of Salesforce are global variables used?
What are the most commonly global variables in Salesforce?
What are Formulas in Salesforce?
What are the pros and cons of using either SAP C4C or Salesforce CRM?
If the app that we would like to connect to Salesforce does not have an open API, is it possible to still have an integration?
How can we display Images stored in Documents object on VF page in Salesforce?
I have a custom application in Salesforce classic. Will I need to build a component from scratch to move it to Lightning? If we have a Visualforce page, how easy is it to convert to lightning component?
What are the differences between Files and Attachments in Salesforce?