Do they use hep lock in picc line?

Yes. Typically in piccs without a valve. Ones without a valve can become filled with blood that clots. Heparin helps prevent the clot. Piccs with a valve does not allow blood to enter and can be flushed with saline. Piccs with valves that are not working well can be locked with Heparin to help their function.
Sometimes. Heparin locks are frequently used, but other locking solutions (such as saline) are also used. It's not clear if any one locking solution is better than the others (or if specific patient populations might benefit from a particular solution). There's also a variety of different hubs/connectors that may be used.