Very surprised to see תהיינה here! Call the 1960s, it want's its conjugation back :)
The conjugations of the 60' were the best, everybody knows that.
uhh yeah what is this? can i basically ignore it and just assume that i'll see תהיו everywhere?
You can totally ignore them, but TBH 3rd ps, f., pl. conjugations are so easy you'll get them instantly when you come across them in historical or very high register text.