Some questions about web publishing. (Affiliates/Ads/Trademarks)

For instance, if I had a blog, and posted a text-link to another company’s website, I’m sure that is all legit (as long as I wasn’t doing anything illegal). Who doesn’t love some free traffic? But would these companies frown upon me using their logo/name as an image link?

I’d be creating a menu of some sites and this menu would contain links of all the same size. Therefore, I’d have to do some small edits to those images. What are my limitations on this? I wouldn’t edit the image itself, as in change the colors or anything, but just cropping and resizing, and possibly only using their logo, and not their name, or vice versa.

For Ads, is it required that I create a designated label where these links are, such as “Advertisement” in small words above the group of Ads? If so, would it also be required for affiliate links? I seem to only notice these little labels on CPC Ads.

When linking to an affiliate, am I allowed to remove their image or modify their advertisement’s wording and just use their name to link directly to them? For instance, some offer text links, but they are like “15% at whatever.com. Use code: kiens08” Can I just put a link “whatever.com” as an affiliate link?

Are there limitations on posting links/affiliate links/Ads that may cause a conflict of interest? Say I post a group of various popular dating sites’ affiliate links or Ads on one line/coumn, would that be an issue? Would it differ if they were only text links (not seeking revenue)? I can see why, but I want to clarify and understand my limitations.

Thanks in advance! These are some things I have to know before moving on.