Hello,
1 & 3 - Yes. You have to configure the actions in the "plan".
The "group subscriber" plugin allow to select groups which will be add or remove to the customer depending the status of its subscription.
2 - In the HikaSubscription configuration you can set-up the email renewal emails ; these settings can be override per plan.
And the email can be customized as other HikaShop emails.
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.