1. 2NT response to 1 of minor without previously passing Natural (13+, balanced, unlikely to have 4 card major) Non-standard. SAYC says it's 13-15, although most who claim to play SAYC don't know that. Just about everyone else plays it as 11-12. 2. 2NT response to 1 of major without previously passing Jacoby is near universal. 3. 2NT response to 1 of minor having previously passed Natural (11-12, balanced, unlikely to have 4 card major) The same as by an unpassed hand, but frankly not a bid I'd make very often. If you think your hand is that good, maybe you should have opened? 4. 2NT response to 1 of major having previously passed Still Jacoby for most people. 5. 2NT overcall of 1NT 2NT does not exist in DONT.