It is the same case even with condition activity as well.

Journey Optimizer requires events to be streamed to Data Collection Core Service (DCCS) to be able to trigger a journey You can refer to the following documentation for more detailshttps://experienceleague.adobe.com/docs/journey-optimizer/using/configuration/configure-journeys/events-journeys/about-...

This is not feasible - you will have to use a middleware to interact with the decisioning API   

Update is not feasible but a new profile will be created if the "Create new profiles" option is selected. In essence, among the millions of transactional messages intended for known recipients, there may arise a need to send some to unknown individuals. For example, if a user attempts to reset their...

No, we don't have these API's currently. This information can be retrieved by querying journeys system dataset

We have channel level reports https://experienceleague.adobe.com/docs/journey-optimizer/using/reporting/channel-report/channel-report.html?lang=en#:~:text=The%20Channel%20reports%20provide%20users,across%20various%20campaigns%20and%20journeys. but nothing specific to the fragments.

I believe customer should be having a monitoring tool (say, for ex:- Prometheus / Grafana / Datadog etc.,) which their IT team should help assist with. 

You can host fonts on publicly accessible website (ideally you brand website) / CDN  and use those public URLs directly in CSS in the HTML. You may also want to enable CORS on the server where the fonts are hosted

You can trigger the journey in test mode to a specific profile and then share the mirror page link to the relevant stakeholders for review. Exporting emails as a jpeg / png is not an option. With respect to integrating Adobe work front fusion and adobe journey optimizer, following documentation high...

Not on the AJO side, this needs to be monitored on the customer side to understand how frequently the authentication end point is being hit.