question about a good backlink opportunity

I have come accross a good opportuinity (or so i think) to create a high quality backlink.
A friend of mine has a pr3 web site which he is not usiong for organic traffic, just to have
an online presentation of his company. And he gave me the permission to place backlink
to my site. Please note that his site is about food product and my site is completly different
niche: games. Currently the site has no links to other sites at all.

So here comes the questions.

1) My site is a blogspot one month old and just started to create
backlinks. will it be useful to place a backlink to the pr3 site? Also there is a catch. I must place
the link in a place that is not actually visible as it is not related to my friends product at all.

will it be ok if i place it within comment tags in the html code of one of the pages?
for example<!-- website address -->

2) could i put backlink for 2 of my sites or it would be better to put only one backlink?

3) Any way to make those backlinks follow?

Looking forward for your reply!

Man, it's one backlink... Just put it on some inner descriptive page with pr 2+ saying "a nice website of my friend on gaming: [...]"

I wouldn't go for a backlink directly on the root page, since this would lower your friend's consumer trust.

thank you very much. if i may ask how would it lower the trust if its not visible?
I ask because its a friend of mine. i would nt want such a thing to happen...

EDIT
also not possible to put it as u proposed. the link must not be visible...

Don't stress too much about that one link. Just make sure that you find some connection between yours and your friend's site (he mentions games on his site in some way) and you are good to go.

Thank you my friend.

PR3 is nice.
Don't make your link invisible. To make it natural you need to put some text near the link. You can write some nice and interesting article - use your fantasy. That's not a problem if your website is different niche. And yes, you can put 2 links, why not if there are no links on your friend's website.

I agree to starway.

Furthermore, invisible links are against the search engine guidelines and may harm (even if only a little) your friends site.

To come back to the consumer trust: What would you think if you would like to purchase a reputable(!) service and on the main page there is a link to a non-related website? Sure, may not be a huge influence but why should you make your friend take the risk?

thank you very much guys. Your help is very valuable for me..