Can second hand SIM locked iPhone 4S be activated with a different carrier?
1 Question: I am wondering if this is standard to get T&amp;C on the
  screen after restore or this phone never been activated?


Yes it is standard to get the T&amp;C after restore.


  2 Question: If this iPhone has never been activated - can it be
  activated with a different carrier's SIM card to what it was supposed
  to be locked to?


Activation is irrelevant.  You'll either need to jail break the phone and unlock it, or ask the carrier the phone was intended for to unlock it.


  3 Question: If I try to activate it with a SIM card from a different
  carrier - what is the chance that it stops working and becomes a
  "brick"?


No, inserting a SIM card from another carrier won't "brick" it.  It just won't work in the phone.

Something to consider, the iPhone 4S uses a smaller sim card than standard phones do.  When upgrading to a 4S from a 3GS I had to sand my SIM card down to fit (I like to use prepaid service so I'm not under a contract).