any way to read DATA/ directory's CONTACTS.DB?
What you read is about correct: contact is stored in /data/data/com.android.providers.contacts/databases/contacts2.db.

You will only be able to read /data if you're rooted. Although Android 4.2.2 should be easily rootable by now, the fact that you're stuck in the boot logo (likely a bootloop) means you can't keep a stable ADB connection, therefore no rooting tools would work (requires stable connection for minutes).