Script logs are automatically trimmed to a length specified in CJ Settings.
What's the difference? Old Backup exists only for backward compatibility with very old script versions. Use MySQL Backup instead. All script data lives in the database, so transfers are done via MySQL dump. MySQL Backup is a standard MySQL dump that excludes referrals and language/IP statistics to save space. This is usually fine for transfers, but if you need that data, ask your admin for a full dump.
If the MySQL database encounters issues, the script attempts self-recovery. If that fails, you can click the Repair button. (In practice, this is rarely needed.)
Log of IP addresses that accessed the admin area.
Reset the entire CJ. This deletes statistics only; it doesn't affect trades.