Article in English: There is no sort of change or setting you can switch before opening an image that unlocks the background layer. Just open up the image like normal. This is the long box on the right of your screen labeled layers. You'll see each layer -- starting with "Background" -- as well as a little thumbnail of the image. Next to Background there should be a small padlock icon that tells you the layer is locked. 'Troubleshooting: I don't see "Layers:" Click on "Window" in the top bar. Make sure "Layers" is checked. If it is, and the palette is still not open, click "Window" → "Workspace" → and hit "Essentials." Still struggling? Reset "Painting" and click that. This is perhaps the safest way to go, since it saves you a perfect original copy if anything goes wrong. For PC users, press Ctrl+J when the background layer is highlighted. For Mac users, it is Cmd+J. Your new layer will be unlocked and ready to edit. You can also click on "Layers" from the top bar, then click "Duplicate Layer." Simply double-click on the title of the layer, "Background" and it will open a little box to recreate the layer. From this box, you can:  Change the name Set a blending mode Color code the layer for organization Set the layer's base opacity In the top bar, click on "Layer"-- the right option should be near the top. Simple and easy, this also replaces your background layer with a brand new one. You will not have a spare background, just one unlocked section.

Summary in Vietnamese:
Mở hình ảnh trong Photoshop như bình thường. Nhấp vào lớp bị khóa trong bảng "Layers". Nhấp vào lớp và nhấn Ctrl/Cmd + J để nhân đôi phiên bản không bị khóa của ảnh nền. Nhấp đúp vào lớp nền để đặt lại tên và mở khóa. Nhấp vào "Layer" và chọn "New Layer from Background" (Lớp mới từ nền) để tạo một lớp mở khóa thay thế.