Hi, Michael!

Thank you for your interest in Amelia.

1. Is it possible to block (multiple sessions spread across multiple days) book an appointment? - Could you please provide us with more details about your business? So we will see if Amelia can match the requirements.
2. Waiting list for an unavailable time slot? - Unfortunately, there's no waiting list among current built-in features in Amelia at the moment. 
3. Are user able to pay for an appointment during the booking process? - Yes, we have the following payment methods in Amelia: Stripe, PayPal and WooCommerce integration.
4. Are appointment cancellation and rescheduling possible? - Yes, sure. Both Employee and Customer, can reschedule or cancel an appointment if you give them such permission. One of the options is to do it on the Employee Panel or Customer Panel respectively.

Looking forward to hearing from you. 

Hi, Michael!

I apologize for the delayed response.

1. The business is a counsellor/psychologist company that provides services to individuals and other companies(or businesses). Companies especially book multiple sessions over multiple days so that their staff can use our services, we need a feature that allows this. - Unfortunately, it's not possible to book multiple appointments at once with Amelia current built-in features. However, something similar can be achieved through Recurring Appointments or Packages of Services. Basically, Packages is a feature that allows creating packages of multiple appointments (of the same or different services). In that case, the services that are included in the package and the number of appointments will be fixed, and the price will be set for the whole package. Please note that Packages are available only in Pro and Developer license. 

2. I'm assuming that admin will be able to fully manage appointments and our services? - There's another role in Amelia that has rights to add Employees/crete Services - Manager. This role is similar to Admin but has no rights to delete any information. Also, if you want to give your Employees more permissions, you can use some plugin for roles setting - for example, User Role Editor.

3. Also, would customers be able to book appointments as guest and registered users? And does the customer access use the WordPress login/registration functionality? - Customers can book appointments with and without being logged in to WP. However, Amelia doesn't have a membership functionality that would keep the Customers logged in and will require registration before booking. Nevertheless, in Amelia, Customers can be registered after their first booking, and after that, they will be able to log in to the so-called Customer Panel on the front-end to see their bookings and manage their appointments (if you give them this permission). You can see how the Customer panel works here. 

Please let us know if you have any other questions.