On the first point, see Transform > Count Values within Cases (COUNT) and select system or system and user missing as the value to count. Then you can use Data > Select Cases (SELECT IF) to delete cases with too many missings.
For the second point, you will have missing counts from the first step. Then with the file sorted by name and the count and SELECT IF with the lag function, you can pick out the cases to keep. Exact syntax depends on details such as whether there can be more than one duplicate for a case.
=====================
To manage your subscription to SPSSX-L, send a message to
[hidden email] (not to SPSSX-L), with no body text except the
command. To leave the list, send the command
SIGNOFF SPSSX-L
For a list of commands to manage subscriptions, send the command
INFO REFCARD