discounted Hikashop products for registered joomla users
This probably being the only thing am unsure of. We don't have any direct integrations with Hikashop, but CBSubs comes with CBSubs SQL Actions for letting you run custom database queries based off subscription state so that could be used to create a Hikashop promotion. CBSubs can also add Joomla usergroups based off subscription so if you have a promotion in Hikashop that's limited by access that could also work.
Membership is based on calendar years, not on "1 year from membership start".
Yup, that's doable. We've "by calendar" durations specifically to cover such usecase.