Not in the current state (with respect to all the three attributes). Kindly log an enhancement request for this.

Journey status is currently not available

You can query journeys dataset and status, created by are not available in the current state (as you have already mentioned)

No, complex data types (array in your context) cannot be updated.

You can either put a condition like .....pathToPlanId != '' or remove the filter if you want to count all of them in ObjectLevel4 array object by specifying ...pathToObjectLevel4.all()}

You can validate it on the following lines listSize(#{ExperiencePlatform.ProfileFieldGroup.profile._ObjectLevel1.ObjectLevel2.ObjectLevel3.all(currentDataPackField.PathTofieldWithinObjectLevel3 == '<filter value>'). pathToObjectLevel4.all(currentDataPackField.PathTofieldWithinObjectLevel4 == '<filte...

Alerts are supported for two specific cases as mentioned in this documentation https://experienceleague.adobe.com/en/docs/journey-optimizer/using/reporting/alerts You can potentially leverage query service https://experienceleague.adobe.com/en/docs/experience-platform/query/clients/overview  and con...

which API end point are you using ?

In emails, you can use an expression mentioned in this post as the syntax is different https://experienceleaguecommunities.adobe.com/t5/journey-optimizer-questions/how-to-get-the-last-4-digit-from-a-string-in-ajo/m-p/698651#M2616 

You can validate on the following lines and what ever satisfies this expression are the profiles who have EML value in the exclusionType string array and the complement can be used for not EML population.in('EML', {ExperiencePlatform.ProfileFieldGroup.profile._abc.customerAttributes.exclusionType})