can I explore after final mission?

[J. Carmine]

I collected all the artefacts and got the notification that its the final mission of the main story. If I continue will I be able to continue exploring? or will it close off that save file?

[Cocofang]

The endings are self contained. You save the game as you enter the ending sequence and then you finish the game. Afterwards you can just load into the save point and continue playing normally.

[RCMidas]

Also note that there are two endings. One of them requires you to look around a bit for a couple of people to talk to, and then there's a certain choice to make as you enter the final stretch of the game.