The MultiPlus-II from Victron Energy can in principle feed into the grid, but the feed-in is limited to the maximum output power of the device, in this case 2400 W. This means that no more than 2400 W can be fed into the public grid. This means that no more than 2400 W can be fed into the public grid.
The feed-in takes place via the AC output of the voltage transformer, whereby an energy management system (e.g. ESS assistant) is often required for effective control and limitation of the feed-in, which regulates consumption and feed-in.
It is important that the configuration is carried out correctly, for example by assigning an energy meter as a grid meter and making the appropriate settings in the system, so that the feed-in works and complies with the legal requirements.
To summarise: Yes, you can feed into the grid with the device, but the feed-in is limited to the maximum output power of 2400 W and requires a suitable system configuration.