I have many cuttings from this large Coleus Pot which I successfully sun hardened last Summer. Will the rootings & curent seedlings I have growing from it also retain this Sun hardiness for the upcoming Summer??

Welcome to ATP.
I think the hardiness is for each individual plant,
and does not last through to cuttings or seedlings.

My guess is that the cuttings will be fine, maybe not the seeds.

I also believe the plant genetics is what determines sun tolerance.
Do you know the varieties?
If so check with a grower like Rosy Dawn to see how they list the varieties you have.

Once any plant has been inside for a while (a month a more,) the leaves are probably no longer used to that much sun.

Gradually introducing back to outside can help prevent sunburning the existing leaves, and is the conventional advice, but in the case of something that grows new leaves as quickly as Coleus, burning the leaves could be quicker than trying to acclimate the existing ones. That's what I usually do.

If they have retained the same color, leaf angle, and node spacing, they could be OK. Sounds like you have several of each. You could do half each way in case one doesn't produce good results.

Yeah I would take time setting them back outside.. slowly move them into a brighter area.. after being inside they do burn quickly no matter which verity