@Yew Meng I think some of your questions are answered on this thread.
To clarify, you can use the resource or workspace to create experiments provided that you have created the resource before 1st December 2021 and not deleted it after this date.
For students Azure runs a program which helps students use some of the services with free credit. All the criteria and services available are listed on the page.
You can also use the new Azure Machine Learning designer which does not have any dates for retirement. The classic studio is retiring so if you plan to use the services for a longer period it is advisable to use the designer services.
If an answer is helpful, please click on or upvote which might help other community members reading this thread.