ok timestop is successfully cast, 2 actions, all other units are frozen, you have 2 more actions to cast spells, attack, or do whatever you want. at the immediate end of those 2 actions, you have 4 more, and you can do anything you want/are able to do, but you CANNOT case any spells cast in your first set of actions, like timestop. so
if someone was close to attacking you, you cast timestop, than you can do: cast any other spell less than 2 actions, or just attack twice, at the end of that turn, you can cast any spell, or attack or any combination thereof
a great spell, but it is limited, thank god as i do not play the firstborn. it really is a very chronomancer centric spell as it only helps you out