Yes, any 700 * 38c will do the job. The Marathon Plus's could be a bit of a tight fit on your rims - they are on mine. But they will go on with careful use of a tyre lever.

You should have no problems as a direct size for size replacement.

These tyres come in a 700 x 38c size. I had them on my hybrid (700 x 32c) they were fantastic. - no punctures for more than 1 year

yes this tire a great standard for quality

Yes.

Yes, they do ... at least my 700x32C's do, so assume the same for your size.

I know of people who have replaced 23's for 28's. The tyre will come within 3mm of the frame, and yes it will fit even on a shorter wheelbased bike. I have also found it easier to let air out of the tyres when putting the wheel in the frame as the wider tyre can sometimes foul on smaller road type brakes

Shouldn't really be a problem as long as you have frame/brake clearance.

I have 700 x 38 fitted to my Electric Bike which have Mudguards.

The problem is that fitting higher means that there will not be much clearance between tyre tread & Mudguards,

The Max I can get is 700-38 higher causes less clearance smaller feels like you have no tryes on the bike, & going high speed on corners feels like they are coming off the rims.

I don't think I could get 700-40 they be rubbing the tyre treads.

This depends on how much clearance you have and how narrow your guards are. They are bulky. I have 700 X 28s on bikes built for 27" rims so they are OK with wider mudguards in the main.

I have used several different size inner tubes sizes with my tires ranging from 700x38c to 70025c. None have caused problems to date so I would say that it is Ok.

Yes you can.

The MTB version of Marathon Plus tyres only go up to a 2.1 - this being the dimension across the rim. There is always some degree of latitude as rubber is flexible but the difference between 2.1 inches and 3.25 inches is possibly a bridge too far. I can't say for sure. You could buy and return if they don't fit, or try your local bike shop - this is where their advice sets them apart from wiggle!

3.25 inches - what are you riding, some sort of tractor?!

Yes

they are difficult to fit but will fit fine with a bit of pesevererance.

28 wheels are wider in diameter than 700 wheels.

you rims may be too wide for a 28c better stick to your 38c