Which product?

I need a product that will back up data automatically at night for my 3-4 computers. I need this to be done wirelessly. I have a folder on each PC named Data.  I want this folder backed up nightly.  I would ideally like to be able to access backups of the folder for the past 5 days, and then also one weekly backup from the past 4 weeks.  

I also want to be able to store an image of each PC on the external drive for emergency HDD recovery.

How can I get this device on my WiFi?

I am thinking a 4TB MyCloud will do all of this functionality. All PCs are win 7 or 8.

Hello 4thAnd26, welcome to the WD Community. The My Cloud drive should cover all of your needs. Using WD Smartware you can automatically backup several computers and if you have the My Cloud connected to a wireless router, all of the PC’s can access the My Cloud wirelessly. Smartware is unable to create an image of your PC, but you can use Windows backup for that. 

Can I save multiple versions of the folder so that I have options on where to go back and get my old data?  For example - save the last 5 nites backups PLUS one backup from each of the last 4 weeks PLUS one backup from each of the last 4 months.  So at any one time I have the option of getting my data from any one of 13 different versions of the backup.  The software would then also FIFO the backups automatically.  By this I mean that the 5 daily backups are ALWAYS the last 5 days and every day that goes by, the oldest of the five is dropped.  Except that one daily backup is moved to the weekly backup every week.  etc.

I want this feature in case I got corrupt data into the folder 10 days ago, then I can go and restore the file from by backup that occured 3 weeks ago, or 3 months ago.

smartware is pretty basic and won’t do that

you can use a 3rd party backup app for this, as long as it can backup to a networkshare or mapped drive it will work.