I have two questions. 1) Why I cannot edit the posts of the other users and 2) Why I cannot view all the post from Recent Tags?-It shows me : "You are on the Featured tab. There are no questions with an active bounty at the moment. Perhaps you'd like to select a different tab?" my friend can view its but me, I cannot.
In case many of your recent edit suggestions have been refused, you could be blocked from suggesting temporarily; see this question: Account is not allowed to suggest edits. (I think that the same thing may happen if you've made many suggested edits in a short period, but I am not sure about this.)
When I check your last suggested edits, 5 of 7 your suggestions from yesterday were rejected, so this seems as a plausible explanation for me.
About your question 2:
When you view questions you have many possibilities how to view them: newest, top-voted, feature (=having a bounty), recently active, unanswered. If you then choose to view questions only from some tag, then the MSE software provides the same view you have been using previously.
So if you have viewed featured questions on the main site or on some tag, and then you switch to another tag, which does not have any featured questions (at the moment algebra-precalculus is an example of such tag), you will get the message you mentioned:
You are on the Featured tab. There are no questions with an active bounty at the moment. Perhaps you'd like to select a different tab?
The solution is simple - you just choose one of the tabs above: info, newest, faq, votes, active, unanswered. In this way you will get questions from the given tag (sorted by the criterion you choose; if you want to see recently active questions, you click on active). Which is basically what you were viewing when you got that message - you were viewing all questions from the given tag, which have an active bounty. Only there were no such questions at the moment.
(I did not make screenshot, but I hope from the text above and the links, it can be understandable, what I mean.)
The log of your suggested edit (as linked to by Martin Sleziak) shows that your editing activity mainly consists of inserting
\displaystyle at the beginning of all non-displayed TeX formulas. That will either do nothing or render the formula wrong (because it will then be typeset according to the rules for displayed formulas depite not being a displayed formula).
Perhaps you should take the hint and stop suggesting edits that do nothing but break the TeX?
You can't edit other people's posts until 2000 reputation. See the FAQ for a complete description of what privileges you get at various reputation levels.
What do you mean by viewing all the posts from recent tags?