I don't know if you can print it wallet sized from FACEBOOK, But I recommend that you download the picture to your computer (save it) then print it from there.
To keep in your wallet.
yes
It is easiest to download pictures from Facebook onto a thumb drive. The drive can physically be taken into the photo machine at Walmart. The picture and size are selected and within an hour, the phot is ready.
A wallet-sized photo typically measures 2.5 x 3.5 inches (6.4 x 8.9 cm). This size is commonly used for personal identification, such as in wallets, or for keepsakes. It’s compact enough to fit easily into a wallet or pocket.
You can upload a picture of any size and Twitter will automatically resize it.
The image resolution of a picture is broken into pixels. The amount of pixels in the picture depends on the size of the print. There are approximately 100 pixels per inch in a picture.
Press Ctrl, Shift, and the + key until you achieve the size you desire. As well, Ctrl and the - key will make the print smaller.
Right click anywhere on the picture and select SAVE PICTURE AS and fill in name you want it to have.
It depends on a number of things - size, condition, rarity etc.
the same size as your wallet
Measure it with a ruller.
It depends on what picture editor you have. Most have a menu item/feature called Resize. In Photoshop it's in the Image menu. Find it and put in the size you want the picture to print. You may have to change the size thingy from pixels to inches.