How these conflicting scenarios will work in cassandra when one of the mode crashes?
In both scenarios, everything depends on the how long the node N1 was offline, and where the hints enabled or not...

In scenario 1, if downtime was less than 3 hours (default window to store hints), then the changes done when N1 was offline will be replayed, and value will be updated to scott_update2 because this value has greater timestamp. If downtime was larger than this window - then you need to run repair.

For scenario 2, there are 2 things - it could be eventually repaired when read repair happens, or you can explicitly run repair.

But talking about replication - write usually happens to all replicas at the same time, and consistency level specifies how many nodes need to answer to consider request as successful, so N2 could be updated as well in most cases.