when i upgrade to 2.4.0 from admin area. i get all green check mark, it goes through the next step, I skip the backup process. next step it goes through normal process after couple minutes into it, it shows success! but the magento version is still 2.3.5. not updating. any idea ?
The preferred method for upgrading Magento core is to use the command line interface.
You can find a step by step guide to upgrading to Magento 2.4.0 from the command line here