Can you help me with the answers for these questions?

1) Tree plantation camp. Is this term all right? If no, can you suggest the one which sounds natural among natives?

2) Is there any phrase like 'any which way'?

3)We say 'Be kind.' But in a story I came across this expression: 'Be kindly(to the horse). Is 'Be kindly' all right?

How to justify( adverb used in the place of adjective) this usage?

4) In a notice for the students in a school there is an instruction about an programme. Which is better rather appropriate?

The studensts are requested /should to assemble at the playground at 3.
1) tree planting camp sounds a bit better to my ear.

(The word plantation brings to mind a large farm, not the action of planting something.)

2) Yes. It's very informal. Do it any which way you want. A less casual version would omit which.

3) 'Be kindly' seems fairly unobjectionable, but I don't have any explanation that would justify it.

4) On a notice board: Students are requested to assemble at ...

These answers are quite helpful to me.

Thank you very much CalifJim.