Can this Hot Water Cylinder be used with solar water heating?

Yes, This hot water cylinder can be used with a solar water heating system. This Cylinder uses indirect heating via use of a coil. Separating the solar heating water from the houses supply of water, while still allowing the transfer of heat.

Can i use this unit as a spa or pool heater?

The short answer is no. This hot water cylinder is not suitable for use as a spa or pool water heater.