I want to edit a tag wiki but there is not any option to edit on the tag. Why?
Why are only a few options showing?
You are currently banned from suggesting edits due to having too many of your suggestions rejected. It clears in 5 days. Until then, you also cannot suggest edits on tag wikis or their excerpts.
Since tag wikis are slightly different in display (it shows a big black "Edit Tag Wiki" button rather than a normal edit link), the edit button just doesn't show up when you're not allowed to do so.
As animuson notes, you been temporarily banned from suggesting edits. While waiting for the ban to clear, you may want to take a look at your past edit suggestions and see why they have been rejected.
From what I see at a glance, your biggest issue seems to be that you've been making a lot of small formatting edits that not only don't substantially improve the post, but it's not always even clear if they improve it at all.
In particular, please keep in mind that:
For example, compare this edit of yours (which somehow got approved(!) despited introducing a random "