Can I run SU2018 with SU2019 license?

I have an installation of SU2018 with all of my extensions installed. The SU2018 license had expired, so I purchased a SU2019 subscription and have installed it. Some of my extensions are not yet compatible with SU2019. I would like to run my install of SU2018 until this is resolved. Is this possible?

Thank you,

Did you bought a student version of 2018?

Yes, SU2019 Pro student edition.

So the version 2018 was also a student version, which would explain why it expired.
What extensions (V-ray)
By now, most extensions are compatible, anyway…

well, no.