Can I stay in kenya after my wedding next year?

You need to apply for a dependent pass this will be granted if you spouse is supporting you.
This can take a while so you might need to leave and come back whilst it is being processed

An alien registration, or foreigners certificate is not a visa, or residents permit. 

As for above, if your spouse is working and earning enough to support you both, then you can apply for a Dependents Pass.  This will allow you to live in Kenya, not not to undertake any kind of work (paid or voluntary).  It's arguably the easiest way to live in Kenya, but if you really want to work, you would need to apply for a work permit - you are not permitted to hold both types of permit at once though.