The way I understand it-
Resale bought before April 2016 is 100% grandfathered with the exception of the Disney Collection Exchange that was removed from resale in 2011.
Resale bought Between April 2016 and Jan 2019 no longer qualified for membership perks/benefits aka Blue Card.
Resale bought after Jan 2019 continued not qualifying for blue card, and added limitations to tradability. The OG resorts that existed before RIV could still trade with each other but not with resorts added later, and those new resorts/associations would limit their resale to home usage only.
If you bought VGF resale before 2019 (?Jan 19th maybe?), it should be able to trade into RIV.
Any resale bought after that date cannot trade into RIV.