I think you put the assets wrong - I think you missed 3 zeros. Otherwise, Assets of $21M vs. $13B in liabilities would mean a large deficit.
Extending the assets lives allows the liability to decrease (it makes it appear that there is less liability and more assets). The motivation is simple, to make the liabilities smaller compared to the assets. Stockholders look at the sheat and see liabilities decreased by $3M, makes it seems as though the company has less expenses, even though it really hasn't.
As for #4, I don't know the Accounting code of conduct. Sorry.