1. Modern Orthodox often don’t cover their hair . Do you hold the Modern Orthodox to be frum?
They are frum. And are also violating halacha.
1) Frankly, it’s not your business to go around deciding whose gerus is valid or not.
Of course it is. I need to know whether I can marry into their family.
2) The Shulchan Aruch does not actually require a ger to become completely observant before converting. The practice of requiring that is very recent. It makes sense, given current circumstances. But we should keep the basic halacha in mind.
He does require that they intend to become completely observant. Which is no longer the norm. And some rabbis don’t care about this, hence they are not orthodox rabbis.