F5 rSeries appliance firmware upgrade question

Hi guys,

I have 2 x R2800 appliances (appliance_A and appliance_B); each appliance has 1 tenant (LTM). The tenants run HA (active/standby; tenant LTM_A is active, and tenant LTM_B is standby). 

I'd like to upgrade the firmware for appliances and tenants. Below is my planned procedure:

1. Upgrade F5OS for appliance B. Reboot, then upgrade the firmware for the tenant LTM_B on appliance B.

2. Failover to LTM_B (LTM_B will become active after upgraded)

3. Upgrade appliance A and its tenant LTM_A.

Question for #1: When upgrading firmware for a tenant, do I need to upload the image to the R2800 appliance under Tenant Images, or can I just upload the image directly to the tenant LTM_A GUI and start the upgrade from there?

I hesitate to upgrade firmware for both appliances and tenants at once. I'd like to upgrade 1 appliance and 1 tenant first and let them run for a few days in case of any bugs. Is it okay to run different firmware versions for a few days?

Thanks.