under or over, open or closed

I've been arguing this topic back and forth with some very respected TD's and players and no one can get their story straight. The argument is around the criteria for reopening the raising option for players who have already acted in complex situations.

Example 1: 4 players A-D

A: bet 800
B: call 800
C: under-raise all in to 1100
D: under-raise* all in to 1700
A: .....

Q1- Is the 1700 all-in from player D an under-raise? I would say yes as the minimum full raise for player D would be 800 more for a raise to 1900. The counter argument I am hit with from the almighty is that you ignore the 1100 and just treat it as a call. If you think this is the case then player D is making more than a full minimum raise by making it 1600 or more. I have problems with this rule theory as shown in example 2.

Q2- Can player A now re-raise player B? I would say definitely not as no player has made at least a full minimum raise to reopen the option to players A and B and as such they can only call the 1700. It is irrelevant that the bet now facing player A is 1700 which in isolation without player C going all in for 1100 would unlock the raising option for A and B.

Example 2: 4 players A-D

A: bet 800
B: call 800
C: under-raise all in to 1575
D: wants to raise to 1700 with a stack of say 10000 behind

Q3: Can player D do this? I would say definitely not. However this is what is allowable under the 'ignore the under-raise version rule 1.0', I say its total nonsense. The minimum raise for player D has to be 800 more to 2375. Each bet amount including all in under-raises have to 'act' with the action adjusted accordingly for the subsequent players.

Am I losing it, probably. Opinions would be appreciated. Please, no 'Irish style double the last raise' minimum raise requirements.