Hi Winnie,
1. Please refer to the instructions in chapter 5/6 Upgrading .... in the Admin Guide in the CD image (Documentation - System Setup - B1_for_SAP_HANA_Admin_Guide)
2. To upgrade SAP Business One, you must always download a upgrade package to be able to use the upgrade wizard for database upgrade. Make sure you've also gone to the "Updates" section in the download center.
3. For 882H to 9.0H, yes, you need to uninstall everything except for the analytics platform, which can be updated directly. For a fresh installation, you'll also need to download the installation package of PL11 from the "Installation" section in the download center.
Regards