Hello.
Please submit your question at the support forum here http://wpbookingcalendar.com/support/ about aid versions or directly by email support @ wpbookingcalendar.com
This forum is about support of only Booking Calendar Free version.
In any case, here answers to your questions.
1) Here is one important restrictions about the time-slots (10am to 10pm ) and capacity (15 per day)
If you need to make the specific number of bookings per days, then you need to check the Booking Calendar Business Large version, where is possible to make several reservations per specific FULL date(s) by visitors (not time slots). Please read more about it here http://wpbookingcalendar.com/overview/#capacity
At this version is possible to set capacity of the booking resource, so date(s) in calendar will be available until number of reservations is less then capacity of the booking resource. But in this version is possible to make reservation only for FULL date, not a time slots (time slots in this version only record data in the DB, but do not play any logic in reservation). Its means that you can make 15 different per day(s) but not per time-slots in these day(s). Time-slots will be saved to the database as data.
Please read more info about the booking resources and how to configure them here http://wpbookingcalendar.com/help/booking-resource/
Also we highly recommend to check this article about different configuration of capacity and availability http://wpbookingcalendar.com/faq/capacity-concept/
You can deactivate specific week days in the calendar in any versions of Booking Calendar at the Booking > Settings General page in Availability section.
Additionally in the Booking Calendar Business Medium or higher versions you can have flexible functionality for setting available only specific days based on seasons. Please check more here: http://wpbookingcalendar.com/overview/#availability
2) In case, if you need to set discount for week bookings. Its possible in the Booking Calendar Business Medium or higher versions. Please check more about this feature here: http://wpbookingcalendar.com/overview/#valuation-days
3) The Business Small and higher versions of the Booking Calendar is support PayPal (Standard and PayPal Pro Hosted Solution (please note, PayPal PayPal Pro Hosted Solution its does not the same as PayPal Pro)), Authorize.Net, Sage Pay, iDEAL via Sisow and iPay88 payment gateways integration, other payment systems are not supporting yet. You can configure and activate it at the Booking > Settings > Payment page.
If you want to make the integration of your payment system by yourself, so you will be able to check how was integrated exist payment system in plugin like PayPal or Sage Pay gateways. Please check more about this here: http://wpbookingcalendar.com/faq/custom-gateway-in-7-0/
Please note, if you will modify the source code of the Booking Calendar, we will not guaranteed the correct work of plugin and do not support it
4) Booking Calendar support only inline month view calendar where visitors can select specific day(s) to book.
But in read only mode, you can insert the “Timeline” http://bl.wpbookingcalendar.com/timeline/ for showing available and booked days.
5) You can check overview of different Booking Calendar versions at this page: http://wpbookingcalendar.com/overview/
Also you can test live demos http://wpbookingcalendar.com/demo/ to be sure in functionality and do not have misunderstanding.
Kind Regards.