I'm going to address 1 and 2:
Who says that you should rebuild indexes and update statistics? There is nothing inherent to a migration regarding these two operations.
Statistics is included in the database, and there are no format changes between versions (there was in one version change a long long time ago, but that is ancient).
Indexes will have the same fragmentation level after the migration as they had before the migration.
Above assumes that you do in-place, backup/restore or attach/detach migration. Other methods are different since they don't give you a binary copy of the database.
(I know that a frequent recommendation is to update statistics. That is IMO bad recommendation, since people then to believe that you "have" to do it. If you have a 5 TB database and believe that you "have" to update statistics, then that will limit your options for migration (due to the time it takes to update statistics for a large database).)
Addition and hopefully clarification:
A method that gives you a binary copy of the database doesn't require update of stats or rebuild of indexes. Such methods include presenting a disk with the database files (as in your case), backup/restore and detach attach.
Other methods that don't give you a binary copy of the database includes for instance exporting the database to a BACPAC file. We are now in the export/import territory, and the quality of your statistics and external/internal fragmentation of your indexes depends on how things are done by this particular tool so it is impossible to generalize and answer for such tools.
To summarize: Don't believe what you read. You might read some article that say that you should/need do any of these things. You your own understanding and experience instead of just going to what the author of that article say.
