You might try iron out. It removes most rust stains. https://summitbrands.com/product-category/iron-out/?utm_attribute=DMPaidSearchGoogle&utm_term=iron%20out&gclid=EAIaIQobChMIj-G_-qew4gIVTcDICh1Q9gtTEAAYASAAEgJUZ_D_BwE You can buy it at Lowes

You need to figure out what is holding it in place. There may be caulk/adhesive on the back side. Get a thin 1" putty knife and work it between the wall and frame, you'll either find glop of some kind that needs to be severed or a hidden fastener you haven't removed yet. If it's caulk the putty knife should cut through it.

Oh wow, I guess I don't have it so bad....orange stains on the house and fence that you have to avoid, that really is something I never heard of, but it makes sense. So, I wonder if you have ever considered drip irrigation. lol. I have had a fleeting thought about it, every once in awhile, but I think that about the vegetable beds more often. I have no idea why I haven't done it. I did put down some soaker hoses in some areas, but, I haven't used them in awhile. I need to check to see where they are again. Oh, I left them out one winter and they sprung a leak. I just need to replace them, and put them away in the fall. Soaker hoses I am a fan of, but not drip irrigation. I often think that I'm changing plants and shrubs in my garden too often to really get the benefit of 'permanent' drip irrigation. Then it would be one more thing to move. [g] But that's a great idea. That's what I need, is to buy some new soaker hoses at the very least. Thank you. :-)

You appear to have a mounting system known as a tap-in hinge. The hole that is drilled is a little undersized for the ribs on the metal inserts, so that when the two posts are pounded in, they stick in the holes tightly like a ring shank nail. When you want to remove the hinged part, you are supposed to be able to simply unscrew the two screws, and the posts are supposed to stay in the hole for remounting purposes. I don't think the green plastic part is the problem. If the screws didn't back out when turning them counter-clockwise, they might have been over driven when first installed and are jammed onto the metal inserts, or the inserts are turning in the hole. If that is the case, then there is not an easy way to demount the hinge. You might be only able to get it off the way you did, by brute force; but, unfortunately, that sometimes damages the hole and it may not be possible to get new posts to securely mount in the hole because of that. As an experiment, I suggest you try unscrewing the screws for other hinge mounts...including ones you don't want to replace as a test to see if any of the other ones uninstall normally. Here is a video that shows how this works for a similar hinge mounting system: https://www.youtube.com/watch?v=7ekKXVvN6Gg One other thing: with the hinge plate you are holding in your hand, you should be able to put a pliers or ViseGrip on the insert part and then unscrew each screw, preferably with a cordless driver. Whether you can remount the plate securely by reusing the inserts or getting new ones is the question.