At the select tag you have 2 name attribute
<select type="number" step="any" name="actions" id="actions-select" name="wpneo_donate_amount_field" class="input-text amount wpneo_donate_amount_field text">
Then, when you submit, it only collect the first defined name. (name=”actions”). You have to delete this attribute. and using name=”wpneo_donate_amount_field” only.
It should like
<select type="number" step="any" id="actions-select" name="wpneo_donate_amount_field" class="input-text amount wpneo_donate_amount_field text">