Odds of flush on flush

What is the chance of flush on flush with a single opponent?

And hitting the flush?

Both player have suited hole cards (same suite).

Your chance of a suited hole cards is 12 / 51 = 0.235
Just short of 1/4

Opponent same flush - two cards

combin(11,2) / combin(50,2) = 0.045 = 1 / 22

Chance you (both) make a flush by the river = 0.0393 = 25 : 1

This includes 4 and 5 on the board so another player with with a single flush could win.

You make a flush on the river with 89s only 3 on the board - what is the chance you opponent has an over flush?

If they play any two flush then like 2.0% but they are not likely to play like QJT little or under T and not connected so like 1.5%.

Opponent same flush - one card

Let's say one card and T or greater
You are playing 89s

Opponent chance = 5*39/50 = 0.16
That is random

If your opponent is only playing A-T then 0.40 chance they have single flush (higher than you).
Well pair are also in their range - but then they can make a boat to beat your flush so that is about a wash.

Make flush with the board only showing 3
You are safe as there cannot be an over flush
0.044 = 21.63 : 1