If the jam is runnier than the cream, the jam goes on top.
If the cream is softer than the jam, the cream goes on top.
Make life easier for yourself.

I make tea in a pot. I put milk in the cup before the tea because it mixes better, so no need to stir (no sugar for me).
The idea of a teabag floating in milky liquid in a mug is so revolting I prefer not to think about it. So if I am somewhere without a teapot or a suitable jug it is certainly milk in last, AFTER removing the teabag.