I want to know, using RB433AH routerboard with 2 r52h wireless card. Is it possible to use same frequency "2484" on 2.4Ghz with same band for point to multipoint network through sector antenna at same location.

I want to know, using RB433AH routerboard with 2 r52h wireless card. Is it possible to use same frequency "2484" on 2.4Ghz with same band for point to multipoint network through sector antenna at same location.

No.
You can, but the performance will be rubbish!
They will interfere with each other.
You need to select non-overlapping frequencies for each radio.

Some of my clients "P throughput" drop down and up every second when they are on and sending or recieving traffic from my network and they are not getting full bandwidth and their "ping ms" goes very high. I don't know the exact issue. Please help me.

If you have two cards in the same band on the same board you need to lower the tx to below 20dBm, lower than that is better.

At full power an R52H can see another R52H on the same band at -25dB, which even if the channels are far apart (5260 to 5825) they still cause significant problems.

Drop the tx power as low as you can make your links reliable, or preferred, put each radio on the same band in a different metal enclosure as far apart as possible.

I would also suggest enabling hw-protection on both cards if you must use the same frequency on both. try cts-to-self first, and if you still have problems try rts-cts. also enable adaptive noise immunity