Integration Portal 365 in an existing portal

Hello,
I have some questions about portal authentication.
My customer portal is currently being developed under PHP / Symfony.
I would like to replace my current authentication with that of the contact-based Dynamics 365 portal. Is it possible ?
I would also like to add the possibility of creating incidents and to follow them by integrating the portal 365 in my current portal. Is it possible ?
Is contact-based authentication compatible with OAuth2? If so, can I use it to connect to another OAuth2-compatible site?
In thanking you,
Nicolas