1. I don't quite understand what you mean.

If it is in the picture you made. You want to add some other pictures. Then just open the image you want to add. Then just drag it into the picture you are making.

2. You can use the marquee tool to create borders.

3. Beginner to PS. Your best bet is to open two canvases. Then put the picture you want into it. A blank. First select the part you want to use with the marquee tool. Then use the drag tool to drag it onto the blank canvas. Then use CTRL+T. Freely zoom pictures. After resizing it to the size you want, right-click and rotate. Adjust to the angle you want. Just make sure. You can click on any tool and it will prompt you whether to apply it. The same goes for the second avatar. Then put the two avatars together. Just turn down the transparency. There is transparency in the layer tools.