I don't know if there's any official clarification but I haven't seen any. Here's how I would, after a brief skim, run it:
You don't need specifically accept or deny. You know the same way you know anything else, so unless you're really into being the God Police, you probably just cut off anyone who specifically bothers you. And you can have as many worshippers as you want, I guess.
All this has to be dealt with from an RP standpoint. There are no "rules" per se. You RP collecting followers, and convincing them to worship you instead of...anything else. If some of those followers are Clerics (or maybe Warpriests) they can receive their spells from you, up to a max spell level equal to your tier and can select from the domains you offer.
You likely don't have to respond to every request to cast a spell, but you would likely have to respond to each person requesting spellcasting from you (i.e. I want to be a cleric of Moppy, Moppy has to approve me as a Cleric, but does not have to approve all spell selections I make).
To know if someone is naughty? Kind of up to DM on how to handle that... I would say you supernaturally "know."
You can have as many worshippers as you can have people worshipping you. In other words, your number of worshippers is limited only by how many people you can convince to worship you. You are semi-divine, so some things that seem beyond mortal power/comprehension are now in your wheel house.
TALK TO YOUR DM
If you are the DM, make up your own rules, since that is what the DM gets to do.