Quote from: aleksej996

Nodes don't accept double spend transactions, at least the Bitcoin Core ones don't. Instead the return an error saying there is a tx mempool conflict.
Nodes don't accept conflicting transactions and they do not replay them, so a second transaction would only be available to the nodes that came online after the first transaction was sent or discarded the first one due to it being unconfirmed for too long or something like that.

Bincoin is not Bitcoin core client it's a protocol. So if transaction is valid according the rules it's valid transaction. Even now you can submit a non-standard transaction to miners and it will be accepted into block.

Quote from: aleksej996

To me both of these ranges seem artificial and make no sense. On average block is mined every 10 minutes and if everything is working correctly in the future, optimally all transactions would be added in the very next block. So depending on when transaction was published compared to this this period between two blocks, it would likely be 5 minutes on average.

Blocks will be full in the future too. Even with level 2 solutions in place. If blocks would have empty space then on chain fees would be near zero. And how would miners get paid at this case when block subsidy become 0? So 10 min. it's for highest paying transactions only even in the future.

Quote from: aleksej996

I am no quantum physicist, but I don't think that quantum computers work like that, not like classical ones. Completely different story.
As I understand, quantum computer will either do the job practically instantly or will not be able to do it at all if it is not big enough.

Here you are probably right. If it will be possible time constrains would not be matter.