Verified status isn’t for bots on a single channel, it’s aimed at bots that need the rate limits to operate on a large number of channels on the platform. A bot operating on a single channel should never come anywhere close to the limits and need verified status.
Regardless of any status your bot may get, whispers are not something your bot should utilize, they are unreliable to the Twitch’s spam prevent measures and things of that nature, so even verified bots can in no way reliably send whispers, so you should design your bot to either use chat, or to return information to the user through your extension.
Extensions don’t have ‘verification’ or anything like that. If you want to use the extension on your own channel then just add your channel to the allow list, and go through the review process. Once it passes review only your channel will be able to install it, and viewers can interact with it on your channel.