Creating expressions using experience events will no longer be supported in the expression editor used in journey conditionsReference -  https://experienceleague.adobe.com/en/docs/journey-optimizer/using/orchestrate-journeys/journey-use-cases/exp-event-lookup Example (Note this is not recommended) -...

You can take a look at this related thread https://experienceleaguecommunities.adobe.com/t5/journey-optimizer-questions/offer-decisioning-via-web-channel-in-ajo/m-p/687306 

Kindly try this (upper(substr(#{ExperiencePlatform.ProfileFieldGroup.profile.person.name.firstName}, 0, 1))) + (lower( substr(#{ExperiencePlatform.ProfileFieldGroup.profile.person.name.firstName}, 1))) + ' '+ (upper(substr(#{ExperiencePlatform.ProfileFieldGroup.profile.person.name.lastName}, 0, 1))...

You can create an audience checking for sent email status and a specific journey version Id and leverage the same audience using inAudience() function 

(upper(substr(#{ExperiencePlatform.ProfileFieldGroup.profile.person.name.firstName}, 0, 1))) + (lower( substr(#{ExperiencePlatform.ProfileFieldGroup.profile.person.name.firstName}, 1)))You can validate using an expression on the above lines

One of the approaches is to start the journey with add to cart event, wait for x mins, check using streaming segment if there were any cart removal or purchase events in the last x mins (and if so, suppress), else send the cart abandonment email https://experienceleague.adobe.com/en/docs/commerce/da...

You can take a look at this related thread https://experienceleaguecommunities.adobe.com/t5/journey-optimizer-discussions/how-to-fix-error-email-personalization-not-allowed-in-domain/td-p/676506 

You can explore the options detailed in this documentation https://experienceleague.adobe.com/en/docs/journey-optimizer/using/configuration/archiving-support 

Kindly take a look at this documentation https://experienceleague.adobe.com/en/docs/journey-optimizer/using/orchestrate-journeys/create-journey/testing-the-journey where in you can use test mode to validate the journeys (either audience qualification or read audience based) There is also a dry run f...

I would avoid using it as it is an internal dataset and not publicly available and can be changed any time breaking any integrations built on top of it. https://experienceleaguecommunities.adobe.com/t5/journey-optimizer-questions/query-the-journey-properties/td-p/710026