no
Im not sure, but if anything its the format you downloaded it in, it proberably doesn't work with your ipod..
ITunes
There are many ways to download between iPod-Computer and Vice Versa. If you want to put something from your iPod to your computer, you can connect it to your computer, and in iTunes, right-click on your iPod, and click "Transfer Purchases". Once those are all downloaded to the computer, you can drag them to a new iPod!
Yes.
No.
mp4
yes you can what i did i downloaded boombot to my pc then i conveted the format and now i play it on my ipod
podcast
Yes, you can put music on a jailbroken iPod Touch.
Unless you "Transferred Purchases" to your iTunes or made a backup of your iPod, there is ABSOLUTELY no way to.
If u have itunes put the song in itunes. connect ur ipod to ur computer with the usb cable. Then go on file in itunes and go down to sync ipod. When you plug in your Ipod after you have downloaded the song, the song should transfer onto your Ipod. If not, find the song in your music library, and drag it to your Ipod folder. That should work!!