Can I Clear/delete all comments which is posted by me? I know I filter It from Activity>Comments Tab But It has about 9 pages. so it is difficult to delete one-by-one.
So, How to delete all comments? Is it possible (permitted)?
No, I don't think deleting all your comments is a good idea. Manually or otherwise.
While comments in general are considered to be transient (and less important than answers), they often form part of a conversation that gives context to a post. If you blanket-delete your half of that conversation, you're removing part of that context and making the comments less useful.
More than anything I don't see what you get from deleting content. It's not as if it's counted against you.
To be clear, some comments become obsolete, redundant... But you find those by checking up on old comments, and reading the replies... Not going on a blind deletion spree.