Log Shipping with Database Snapshot for Read Queries
(1) While restoring log every 30 min, I assume we cannot take snapshots on databases which are currently restoring, is that true?


Yes, all users has to be disconnected before the logs can be restored. 


  (2) So plan is to take snapshots, when transaction log backups complete. If I have snapshot, and another transaction log restores
  occurs later on database, will be snapshot break or continue to
  operate normally?


This depends on how you setup your Log shipping session. While setting up the Transaction log shipping, you have the option to Forcibly disconnect any users connected to the database or wait for users to disconnect, before the logs can be restored. But either way all users must be disconnected before the transaction logs can be restored. 





Depending on your business needs (Preferably, get the business people involved in this decision) you can set the precedence for Log restore or Snapshot.