How will different builds effect the game

Just Wondering
If a Gold if member is on TRS2019 build 3 ( they get everything first )
Silver member is on TRS2019 build 2 and
Installed from DVD either Trs2019 build 1 or 2

What happens if a Gold member uploads to the DLS with build 3 route for example
Can you install and run that route if your on a lower build number
Also the uploaded item may not be the next released build number it could be build 5

Currently anything created in a higher version is not compatible with an earlier version. Resolving this is something we're working on.

Is this for routes only? or sessions also?

ie: I download a freeware Route (v 4.6) from CM and using Trainz Plus (build 3) I create a session, that session only works with Plus build 3 or higher?