Purple punch

I limit my max temperature to 85f (30c) in the top of my tent in summer and don't notice much difference in yield versus winter when my temps are lower. But, 88f (31c) really isn't bad. Keep in mind that these plants evolved in some really inhospitable climates. A hot, dry almost desert with the occasional goat herder pissing on them and they still grow. But, as the temperature goes up you need to pay more attention to where and how you are measuring temperature. A thermometer will see a very different temperature than one at the top of the tent, and different than one at the top leaves. If you're getting 87f at the top of your plants I wouldn't loose sleep over it. Do whatever you can to lower the temp a bit but don't let 88 scare you.

Yes, at these high temps photosynthesis efficiency will decrease and given you're in flower you risk negative effects such as hermaphroditism, foxtailing, wilting etc. If it's unavoidable, make sure she's well hydrated; then hope and pray.

yes i think it will .unless u use large amounts of water very often but even then the plant may slowly burn up