For #1, you are considered to have paid the money the day you put the check in the mail. As of that date, you no longer have "constructive receipt" of that money.
What I do with my business checks, they have on them "VOID after 90 days". So if the check is not cashed within 90 days after the date on the check, it's no good. When t hat happens, I just add it as business income for whatever tax year the check becomes invalid.
