I have created 2 events with same name 'purchase' for universal analytics and for GA4 but the monetisation report is not correct in both the dashboards.
How can I create purchase event for both Universal analytics and GA4 and show the correct transactions in the report?
Also Can I create custom events like order tracking with product(item) parameter like purchase and create a custom report with all the parameters in the GA account?
Are you using a datalayer push for the ecommerce data that you want to display in your Analytics?
Or are you using dynamic values that you scrape from your website with custom javascript variables?
In any case, you have to include the correct structure in an event for the correct report to work.
I would recommend building a correctly formatted datalayer.push event that corresponds to GA4 standards.
For example: How a purchase event should look like: https://developers.google.com/analytics/devguides/collection/ga4/ecommerce?client_type=gtm#make_a_purchase_or_issue_a_refund Required and optional event parameters: https://developers.google.com/analytics/devguides/collection/ga4/reference/events?client_type=gtag
Then you can use a GA4 event tag to capture ecommerce data from the datalayer, and the UA tag has a checkbox that enables it to process GA4 data found in the datalayer.
This approach means that you will only have to support one type of Analytics structure on your website while you get ecommerce reports for both platforms.