I want to calculate exitRate, dropFromPage, PageTime and pageImpression using GA4 API Beta version mentioned below Analytics Data API Overview
However I have not able to find any metric for the same in documentation.
Any Idea
https://developers.google.com/analytics/devguides/reporting/data/v1/api
But these metrics are available in Google Analytics V4 UA Dimensions & Metrics Explorer and core reporting api
Why does GA4 reporting API Beta version does not have metrics that available in reporting API V4?
First off there is no Ga4 reporting api beta. Its called the Google analytics Data api and it is currently in Beta test. This api is used for access data behind google analytics GA4 accounts. It only has access to metrics for GA4 accounts.
The Google Analytics Reporting api v4 is used to access data behind universal analytics accounts not GA4 accounts.
GA4 and Universal analytics are not the same system and do not have the same metrics.
The first thing you need to understand is that there is a difference between Universal analytics and Google analytics GA4.
The old Universal analytics systems can not be compared with Ga4 they are not not the same and they are not completable in any way.
Univeral analtyics
So checking for your dimensions and metrics in the universal analytics UA Dimensions & Metrics Explorer is not going to tell you what is available for use with ga4.
To find the dimensions and metrics that work with GA4 ou should check GA4 Dimensions & Metrics Explorer
Remember these systems are totally different i don't think you are going to find those dimensions in GA4.
Ga4