This is what I know: If you purchase a Sol-Ark15K, the model on the box should be 15k-2P. That is the latest hardware. It could have a manufacturer date from early 2023. But the firmware may be current. Even if the firmware is not current, as long as the physical model is 15k-2p you will have the firmware upgraded to the latest version which will upgrade to the latest power specifications that are available.
The manual in the box of the inverter is printed by Sol-Ark and placed in the box. This could be from December, 2023 or even later depending on when they, Sol-Ark shipped the inverter to their distributor.
If you are not certain, then before accepting delivery, you can telephone Sol-Ark technical support and provide the model number and SN on the box to confirm if the model is current or not.
208V is available for 3 phase if you connect them in parallel x 3. Otherwise one inverter is 120/240 split phase in USA.