Best Practice for Tier 2 Web 2.0s

Quick questions:
When linking back to Tier 1 websites, is it best to link back to only 1 tier 1 website per web 2.0? If yes, should this be limited to only 1 tier 1 backlink per blog post or per web 2.0?
(I hope that makes sense - I am essentially asking if it is ok to link to multiple tier 1 sites from a single tier 2 site?)

How important is it to use a unique IP address when creating and posting on each web 2.0?

I can tell you that I see people using up to 5 links per Web 2.0 post. I suggest you may put up to 2 links per post. Just create posts with no links to your properties.
Ip doesn't matter unless you are using a platform that is closing accounts easily.

You can use the same IP to create your web 2.0s. The number of links should be limited to avoid diluting the link juice, but you can have several links in each blog post and in each web 2.0 blog.