Temp + OR - Fluctuation

I know the temp should stay steady during fermentation , But however when the yeast is most active during the firs 48-72 the temp will be naturally raised by the yeast crashing and bouncing off themselves , So it might be safe to say even in a controlled environment at 68 it might reach 70 undergoing the fist 72hrs of hard fermenting ...

Question : Lets say THE control 70deg-F , and after the first 72hrs my wort/beer is actually holding at 70 , But after 5 days the temp is sitting at 68
then after 12 days is back to 70 , After 20 days falls to 66 ,After 30 days back to 70 , How will the flavor be affected of this beer by temperature change ?

After the first few days (primary ferm) the temp is not as important as it was (for primary ferm.) You can cold condition or lager in the 2ndary or just age and condition. As for the early ferm spike. I wouldn't worry to much about it keep the ambient temp stable you'll be fine. Next time try pitching at the lowest end of the yeast's healthy temp range to keep it within the good ferm range. The only other option I know of is a thermal well into your carboy with a thermostat dropped into it attached to a heater or cooler. Hope this helps a bit! good luck