Does the luminosity of the hands last through the night ?

Hi, I can confirm that the luminosity of the hands and 3,6,9,12 markers lasts all night but you will need to put the watch under a torch for a while so the lume can charge and therefore,last all night... I hope this helps...

does the battery need replacing?

No need for battery - ecodrive means it runs on light. I have another ecodrive which has run for ten years - great watches

Is Amazon selling fake watches ? No warranty, usually Citizen watches carry a five years warranty.

All Citizen Eco Drive watches have a 5 year warranty. You can register online but there is always paperwork within the box regarding operating instructions, model and warranty. If not ,then it’s origin may be questionable.

Where is that watch made? Is the strap strong enough & can it be used while swimming?

When the movement INSIDE the watch says 'Japan Mov't' this generally means the 'movement' is 'made in Japan'. I would suspect 'other parts' are likely made in China & elsewhere for lower labour costs, than paid in Japan. The watch itself may be 'assembled' from its parts almost anywhere, where-ever the original manufacturer can get the great profit from obviously. As a comparison 'Seiko' - which is also a Japanese company like Citizen is - indicate on SOME model names of watches eg 'J1' at then end of the model name, something like 'SNK601J1' that means this would have been 'made in Japan' because of having the 'J' in the model name. Unfortunately this actual model does NOT have a 'J', since it has a 'K' instead indicating it was likely 'made' in (South? I hope, rather than North) Korea. I have been led to believe 'K' can also mean Vietnam or Thailand/Indonesia too, just NOT Japan. I have only ever seen 'J' & 'K' in model names with a '1' after it (rarely a '2' also). Not all watch sellers even quote the model name fully leaving out the 'K1' or 'J1'. I have no idea how to tell where Citizen watch models are really made and/or assembled. I hope SOME of this helps.