Yes. Kaspersky Total Security has backup and encryption option that can be used to create backup of your files.
AVG Ultimate, Kaspersky and Norton are the best software in terms of secure online transactions.
Yes. Bitdefender and Norton have auto-scan feature which will scan your entire system automatically and periodically in order to ensure security.
Yes, you can have but it is better to choose only one antivirus software for getting effective virus security.
Yes. Avast, Bitdefender and Avira antivirus software have free edition with limited features.
Adaware and K7 antivirus software takes very less time for scanning.