My condo's tiles has hole and little crack, any way to paint/fill up the hole?

Is it still under DLP? If, yes, then go back to the developer

If not, then for wall tiles, can always get the white cement to fill up the hole & crack (assume it is just a hairline crack)
If floor tiles, then use the normal cement... or some colour grount to match the tile colour (can get from tile shops)

no longer DLP. Since the hole quite big, like 10 sen coin... i shall go for tile shops.

Depending where is the affected tile located. If the hole is big like 10 sen coin, then patching up using cement may not look nice, even if you managed to get matching colour grout/ cement.

If it does not look nice, maybe you could just replace the affected tile... provided you can still get the same design..

no choice but use something to cever it... like carpet.

else can try pasting a sticker on the tile
Just like those you find on the floor of shopping mall

Good idea...

Just want to further ask:-
1) any Chemical to wash or polish the tiles? Can recommend the product name and where can buy it?

2) As we know, in between the tiles, there is cement and normally it is white color. Now, most of it is become dirty which showing black. Any product can cover back? I think this should have, like what the contractor worker doing.

If not mistake, they use Acid to wash, than re-lay the white stuff again...
Because one of my existing wall tile been lay different colour (light yellow) and the contractor need to change back to White

thank, hope i can diy it.

Very much doubt that you can just use the acid to wash off the dark cement grout and then replace with new white cement grout. You need to physically "dig" out the old grout.
You may be able to use acid to help "soften" the recently grouted tile joints; but not for old grout.

Cement grout gains strength as it ages..