Answer:
A). 'Birches' is categorized as one of the most acknowledged poems of Robert Frost. The elements employed by him to reflect the impact of ice-storms on Birches would include the descriptions like
'after a rain, They click upon themselves
As the breeze rises, and turn many-colored
As the stir cracks and crazes their enamel.
Soon the sun’s warmth makes them shed crystal shells
Shattering and avalanching on the snow crust'
These descriptions reveal the impact of ice-storms like 'shattering and avalanching' have been detailed through the use of imagery that offers a sensory experience to the audience so, they would be able to connect to it and understand the drastic impact of ice-storms and therefore, 'they would not be able to bounce back'.
B). The major idea behind portraying these radical impacts of ice-storm on the beautiful and serene 'Birches' tree is to reflect the transcendent and accomplished potential of nature to encounter the hardships with strength and vigor. The author suggests that the human conflict between imagination and reality. The carefree childhood represents 'imagination' while the 'ice-storms' reflect the harsh reality of life. The 'unbending' and 'enduring' nature of Birch trees reflect that life cannot be reversed(unbending) and one can only 'hope' and 'endure' the reality of life.