Verified answer

宜しくお願いします is neutral expression which both male and female can use.

There are many ways to say thank you. The common one is ありがとう

That is just very polite and formal, does not got to do with gender. You just wrote in a formal matter.

Both can say that. It not means thanks but "I'd like to ask you to do it.", which is a usual phrase to add at the last of kinda business letter.