"I agree, thank you" or perhaps "Thanks from me too" or "I found it useful too, thanks."

Yes you are right! A hands-on approach means that you are not just watching, you are really doing things, in this case, farming. So they are saying you should come prepared to work on the farm, although of course this will involve more than just your hands!

It's a modern name, so it doesn't have the historic meanings that some English names have, but a quick google suggests that it derives from Cherie, which had a French origin and meant "darling".

"The powers that be" is an expression that generally means, the establishment, the people in charge etc without specifically naming them. "I was going to go out tonight, but the powers that be have changed my deadline for tomorrow so I have to work instead" - means that the managers have changed the deadline. "Our country's laws are dictated by the powers that be" - the government, but by implication other parts of the establishment, control law-making. In this sentence perhaps the speaker is confused that the people in charge should have been on top of the situation and familiar with names and faces, so it was strange that they weren't.

Mist is normally quite a visible, cloud-like weather condition, lighter than a fog, that tends to happen in the cold. Haze tends to happen in the heat, it's less visible than mist and normally due to evaporating water affecting the passage of light. "The valleys were misty, but the hilltops were clear" - you can see mist in the valleys, hazy cannot be used here. "The distant horizon was hazy in the sunshine" - the horizon is slightly blurred, due to water vapour on a sunny day, misty cannot be used here. Hazy can also be used in other contexts: "I didn't sleep well last night and today I feel all hazy" - I can't focus properly.

I think we really need the rest of the sentence to understand this. To me, it sounds like the action plans are ongoing, and they need to be concluded, with "drive" meaning push, encourage, speed up. For example, inventing a first half to the sentence: "The company hired an action plan manager to drive the conclusion to action plans" - in which the manager's role is to get that to happen sooner than it otherwise would.

You would normally just say "thank you" in a general sense, for example showing with gesture that you are talking, or you can turn to each one and say it individually if you like. "Thank you both for..." etc sounds very formal although it could be used and I don't think anyone would have a problem with this from a learner. Just bear in mind - "Thank you both" or "thanks to both of you" are both better than "thank you to both of you" (plus that's a mouthful) and "thanks both" which doesn't work.

You can use after if it is part of a longer sentence, for example "an hour after eating the apple, I began to feel hungry again" You can say after breakfast in the same way "an hour after breakfast we set out on the trip" I think since is used when you are focusing on the event, whereas after helps to situate it in a wider context.