Delayed Onboarding - Recently they have layed off employees. But they are also hiring for senior roles

I was offered a job role of Software Engineer fresher in a middle size startup company .My Joining was on August 2022 , Later they delayed it to December .Few months ago they revoked my offer letter and was told a revised letter would be given and delayed join until further notice .Recently they have layed off employees. But they are also hiring for senior roles. Will they onboard me soon?

It seems that they are not interested. You can do one thing, you may attend interviews and if selected in some other company, join them dropping this offer in hand. Since the company which has offered employment has not allowed you to join, there is nothing wrong in dropping the offer and joining another company of your choice.