Software Engineering is an interesting mix of practice and theory. On the theory side, you should make a habit of browsing / googling for things that are a good intersection of interesting to you and novel. Be forewarned, some of the common places to get information (like stackOverflow) can be very intimidating.
The standard expiration date for most checks is 180 days (six months) and personal checks are included in this policy. In the United States, banks are privately owned and not government operated so banks do have the right to refuse your deposit if there happens to be any suspicion of the item's negotiability.
No. As text messaging is a store-and-forward technology dependent on carriers and their networks, it is impossible to guarantee delivery of a text message. If you are on Pay & Go, the Anytime Credits you purchase will expire after 18 months. If you are on a monthly plan, your Plan Credits refresh every 30 days based on the initial date you started the monthly plan (not on the calendar month). Please note, Plan Credits do not roll over.