If you wish to post externally held pics, or pics uploaded through the old uploader (link at top if page) then you need to use the tags "img" and "/img" not "pic" and "/pic".
Using the built in uploader will generate its own tags, leave them be.

There is a good reason I left both uploading capabilities active......

If you use the built in uploader, then the picture is tagged to the post within which you first uploaded it. You can of course re-use the URL elsewhere, but, if you delete the post where you originally uploaded it, then the picture will be deleted as well.
Pictures uploaded through the built in uploader will stay available indefinitely as long as it doesn't impact on the server disk space.
There is however no way of 'viewing the database' to find old URL's. You would have to find the original picture and right click on it to do that.

If you use the old uploader then as before the images will only be stored for 20 days, but you do have the 'view database' option available.
If you are planning to show a picture in the bottom of your posts, repetitively, for a while, as many do, then I suggest you either host that picture externally or use the old uploader. Otherwise, use the built in one.