Nothing can be said regarding last date of rpvt application form for now because rpvt application form has not been released yet due to covid-19 outbreak and the lockdown caused by it.
Rpvt application form will be released once lock down is lifted off.
Rpvt application form is expected to be released in last week of may.
So , for now you need to wait for the release of application form then only you will be able to know the last date to apply for it.
At this point in time, the RPVT 2020 application forms have not been released yet. They are tentatively scheduled after lockdown period ends. As the current lockdown period completes by May 17th, it is highly unlikely that the applications will be released anytime before May 17th. The applications will be released after May 17th and then the last date will be atleast 20 days after the online release of the forms. Please watch out for official information regarding RPVT.