Pool Tiles - What should be done to prolong life of tiles- inground pool

[nitin100]

Hello

I have a 10mx4m pool (depth average 1.5m) which is now drained due to construction work. This pool was made in 2011 and is of good quality (no leaks etc). This is an inground pool which overflows into channels all four sides. Its middle east and lowest temp we have is 10C(though high is 50C).

I have a few questions - please help (I am not a pool guy - just a home owner so please be gentle)

1. Grout - The grout used was epoxy and is generally ok. Should i use a steel brush to remove dirt and try to apply a thin layer of epoxy again? I will not be able to get the required depth as recommended by epoxy grout (we have mapei available in this region). Or should i put silaxane type generously and let it go in and work its magic? With silaxane type thing work with epoxy grouts. maybe there is something else which i can use (which is available in middle east region)
2. I am removing the 2cmheight sandstone(bad choice - sandstone near pool), because the grating made of concrete is totally dead(decomposed). I am planning to cut a 60cmx60cm tile into 3 parts and fix 2 on the outside and the middle one removable(without holes as I am guessing water will still pass).

Its very difficult to explain - so I have attached a lot of photos. I am looking for suggestion on grouting AND if my plan to replace the border tiles(the cream ones in photo) is workable.

Thank you