"ALSO WHEN DEPENDENT FILES THE RETURN, WILL HE/SHE BE ABLE TO GET FUTURE STIMULUS CHECK? AND CAN SAME DEPENDENT CLAIM THE STIMULUS THAT WAS MISSED?"

Where's the counter? Yet another tax preparer not only doesn't know the requirements, but is letting the client lead the parade.

@ACHUTNEPAL 

You need to Know this and control the client's expectation for trying to dodge the rules.

Perhaps it would help to review what is really happening:

The funds were paid out as Advanced payment against a projection. The projection used 2018 or 2019 tax returns. But 2020 is the Actuals. You use the 2020 return to reconcile what a person is entitled to, against what they got.

If the person is not a dependent in 2020, then they would be entitled to the payment/credit as individual filers. That doesn't mean "not being claimed." It means "no longer qualifies as a dependent."

You might want to bookmark these links and read the IRS guidance.

Interactive wizards portal for determining dependency:

https://www.irs.gov/help/ita

And:

https://www.irs.gov/newsroom/economic-impact-payment-information-center-topic-a-eip-eligibility

https://www.irs.gov/coronavirus/second-eip-faqs#Eligibility

One for each EIP.