trial of PRO of older version of Unity (3.5)

I need to use an older version of unity because I work with a game which is made in 3.5 and it doesn’t work with the latest version of Unity.
Can I activate 30 day trial for Unity 3.5 pro? I only succeeded to get trial of Unity Pro for the latest version and I cannot get it when I downgraded.

Unity Pro is backward compatible all the way to Unity 3.4. You can download all the previous versions here:

so does it mean it is possible to buy pro/plus for older versions ? like in 2018?