In the earlier stage,I imported certain data into the system. Since we add-on more users (sales representative), the data they're trying to import might be duplicated with the existing record. therefore, I have some concerns:

1. Is there anyway the record can track the duplicated record? (Leads, Contact, Account, Potential)

2. Will the new data overwrite the existing record (i.e. activities records)?

3. There are mandatory selections under different custom field, system would automatically create a new context for that feild. Is that anyway I can stop it?

Many thanks if anyone can help!!