What you can build
01Create contacts
02Update deals
03Synchronize properties
04Register activities
A CRM for organizing contacts, companies, sales and relationship activity.
A record type such as contact, company or deal.
A record field such as email, stage or value.
An internal integration using its own access token.
A private app is for your own account; OAuth fits a product used by multiple customers.
Yes, when the account plan and permissions allow it.