The above two missions could be carried out on a dead castle. Infiltrator's Resource Redirection could be done on castles at level 15 onwards and the latter one on a castle level 20 onwards.
A tile sab mission must be done while your enemy is gathering on a resource tile. This could be done on level 15 castles onwards. However, this mission is quite easily intercepted if the enemy is online. Anyway, your saboteur still gain 5 experience if the mission failed.
Now go sab someone 😈😁