Landing pages need profile parameters for identification and are auto appended when you add a link of type "landing page" (in emails)As this is not available in Push/in app - it won't work. Can you share the use case details which necessitates landing page in Push/In app ?

You can try it on the following lines directly using the segment builder (by ignoring the year) and apply a criteria on birth year (say, for example - 1994) and see if that solves your use case.Other way would be to check it in the journey canvas by performing the check of 30 years in the condition ...

You will have to control it using the scheduling options on the read segment / audience journey. Assuming the final node is a message - you can use the message feedback dataset attributes (of the previous journey ) in the audience criteria of the subsequent journey but this means you will have to wa...

If it is an event based journey, you could use jump activity to invoke the second journey. You can take a look at the guardrails here https://experienceleague.adobe.com/en/docs/journey-optimizer/using/orchestrate-journeys/about-journey-building/jump#jump-limitations I am assuming its two different j...

No, journey step events dataset is not enabled for profile and as such, it would not be available for segmentation. Journey step events captures information for every step an individual takes in a journey. A step event corresponds to an individual moving from one node to another in a journey. For ex...

Seed list is internal recipients, isn't it ? So, if you have several combinations to validate in the journey, you can explore the possibility of having separate journeys. If not, you can use the test mode to run it for specific profiles (that are marked as testProfile records)

It is only a single profile that can be specified while running the journey in test mode at the moment. https://experienceleague.adobe.com/en/docs/journeys/using/building-journeys/testing-the-journey  If you need to validate with multiple test profiles, you will need to create an audience of those t...

If you have a REST API exposed where in the marketing eligibility can be checked for each profile, you can explore the option of using custom actions in the journey context 1) Trigger an event which will invoke the journey 2) Use custom actions to retrieve the marketing eligibility for the profile a...

You can have audiences within audiences and specify which needs to be considered for inclusion/exclusion https://experienceleague.adobe.com/en/docs/experience-platform/segmentation/ui/segment-builder#audiences 

You can validate it on the following lines {% let arrayCount = count(profile.productsInCart) %} {%#if arrayCount % 2 = 0 %} even {%else if arrayCount % 2 = 1 %} odd {%/if%}