In general, all save files can be loaded in single-player mode. In Task 2, you need to defeat the golems with Tazar, in Task 3 - skip a turn and defend Castigar's castle (in principle, you can do some other manipulations before skipping), and in Task 4 - land Ciel on the shore and kill the pits.
Maybe someone has something similar or more complex; it would be interesting to see ;)