Measure 2: Stop selling, announcement date (20 12. 1.25.) Those sold before cannot be held accountable, nor can those sold after.
Measure 3: As upstairs said, try to invalidate the other party's patent, such as finding evidence to prove that it existed in the market before his application, or the design picture was published in a magazine, and so on. As long as it is public, there can be evidence to show the time. But it needs some money, at least a lawyer.
In short, it is estimated that it is impossible to get it done without any expenditure.