New fruit trees and bushes

Hi all,

Last year I planted 2 3yr old pear trees and a 3yr old peach tree.

Someone in work told me to take the fruit off as soon as they appear as this helps the tree produce more fruit next year. Is this true?

Does the same go for the gooseberry,kiwi,red grape and blueberry we bought last year?

We have bought a jostaberry this year and would ask same question.

I planted a rhubarb crown last year and it is starting to produce leaves. I have read that I should not harvest this for 2 years. Is this also correct.

Many thanks in advance.