This is a pretty weird question for chemistry as this idea of "infinite time infinite resources" isn't usually thought about, chemistry as a whole usually tries to focus on the most practical solutions to a problem.
For your first question, there are certain limits for what we can create even with infinite time and infinite resources and time due to limits we have discovered, quaternary alcohols for example.
As for your second, I personally think that with infinite knowledge (and thus a complete understanding) of the properties of the atoms and how they interact we could in theory predict any molecule and its respective interactions. But who's to say that we'll ever have that knowledge, one day we may think that we're close and we'll suddenly discover a curveball.
If there is a limit to chain-length and the size of molecules, it has not yet been discovered.