This depends upon how we choose to implement the exchange and the ICO/STO. If the exchange is setup after the ICO/STO ends, then we can use the ICO/STO user accounts database to setup the exchange.
The implementation of payment processing is a separate business case and can be done as a customization request.
Yes, this is subject to the compatibility of the cryptocurrency with the Skalex platform. If the cryptocurrency is not compatible we can add support for this cryptocurrency as a customization.