I see some aphids and some whitefly. I don't know what the bugs that are sticking butt up off the leaves are. Both Whitefly and aphids can be gotten rid of using insecticidal soap sprayed on the underside of the leaves in the eveming hours right before dark. The reason to spray in the evening so the sun and soap combined doesn't burn the plant.

Not good. ACP or Asian Citrus Psyllid are the vector for HLB. Where are you located?

Those are Asian Citrus Psylliids. If you are in CA or FL contact your ag extension office. Be prepared to have your tree either confiscated or destroyed. If you are in another state, heaven help us.

I was thinking aphids, until I saw the white stringy stuff. Sorry you have to deal with this.

What looks like aphids appear to actually be Asian Citrus Psylliid larvae - notably because of those "strings". There is a good video from UC that briefly discusses them and some next steps - https://www.youtube.com/watch?v=UhqwUQm0zpk