1) Trunnions is about a good as name as you'll get I think. They look like lock connections or hoist points when the jacket was installed.
2) They look like cable tray attachment points, minus the cable tray....
3) You tell me what its connected to? Either a drain line or possible a firewater line if there is a submerged pump inside the leg
4) Paint? peeling off of course and so you're down to the undercoat which was usually some sort of zinc rich primer
5) As with no 1 I suspect they are remnants of cable, hook or some other restraint used when either lowering the jacket or transporting it

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Thanks for your reply LittleInch. Your answers are helpful and informative.

3) It seems like a drain line. See 2nd picture in the attachment for reference. But why it is being connected to leg?
4) It looks like a wrapping/specialized coating on top section of the jacket leg where it is connected to the deck. The paint is peeling in this case. You can see on both of the photos in the attached document.

• https://files.engineering.com/getfile.aspx?folder=3a176680-4c8a-4acc-85ac-c

3) Probably connected to stop the drain splashing onto the water (never looks good having liquids pouring off the platform) and also means the inside of the leg is filled with rain water and not sea water. Would help to reduce corrosion. Also if there was oil in the water then the leg would / could act as a separator and you could skim the oil off the top. Maybe.

If its connected to that grey pipe that sticks over the edge maybe its a caisson breather pipe?

4) Very Difficult to tell from a photo what the surface coating is. Could easily be some sort of FBE or high build epoxy or even rubber / neoprene. No way to tell from a photo.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.