Can consensus rules be linked to off-chain information and what are the lock time consensus rules?

In answer to one of your previous questions, Peter Wille I wrote: +2h rule The consensus rule for block approval cannot be a consensus rule because it is based on comparing timestamps with information outside the chain (the actual timestamp).

1. Does this mean that the consensus rules are only those that relate to the data on the chain, and that any rules that are in any way linked to information outside the chain (e.g. comparison, subtraction, addition, or anything related to content in the real world) cannot be agreed upon? Even if we are completely correct/honest, should that be part of the consensus rules because we might perceive ‘something outside the chain’ differently?

2. The consensus rule should be something like this: It can be forever accurate or forever inaccurate, and it is not always possible to become accurate or inaccurate over time. (For example, at what point does a block with a certain timestamp become valid?) When we speak of forever, we do not take into account cases where the consensus rules change.

3. Transactions with a lock time value (set by timestamp, not block height) that have not yet occurred should not be part of a block. As far as I know and what I think so far, this is an agreed upon rule. What I’m interested in is how this can be a consensus rule when compared to the actual timestamp, which is off-chain information.