If you had said 30 to 50 mph, then damage would be possible, although looking at that kerb it seems so low that even at 30mph damage is unlikely

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At 3-5mph the tyre will have absorbed all the shock, and no decent car should have suffered any damage.

On most cars the alignment only affects the front wheels - the rear wheels don't steer so their alignment is normally not adjustable unless your have a very sophisticated rear suspension system.

If you didn't bend the wheel or tire that hit the curb the rest of the suspension should be fine - park on a level spot go behind the car 10-20ft and see if the wheels look like they are parallel and sitting square on the road, then

jack the car up (on the corner that hit the curb) and spin the tire and see if it wobbles, inspect the sidewalls of the tire. The suspension probably worked as designed and didn't cause any damage - you could always take it to a garage that performs front end alignments and have it checked if you are worried.

It is highly unlikely that any damage occured

"He who dances, must the fiddler pay."

I was performing a 3 point turn in a small narrow street and while I was doing my 2nd point(reversing) turn which I think was doing around speed of 3-5mph and had my steering wheel nearly/full lock but I didn't realise on how close I was so when I kept reversing until the back wheels had hit the kerb, which felt quite hard.

I'm concerned if I have damaged the steering wheel system,,steering wheel,tyres,suspension,shock absorber or car mechanical parts or cause the car to be out of alignment?