回答
If you put these two sentence into GT these two Japanese translations are utterly same.
even if these words are synonyms.
I suppose original meaning/definition might have some different meaning/nuance.
I suppose whether you had grasped the difference or not depend on the process that you expand your vocabulary, it would come to be obvious when you try to use the words.
if you grasp it through the process of understanding it.
you'll get not only the meaning/nuance but confidence.
I'd recommend that you'd try to understand the difference by yourself.
at first try it by yourself, then please re-post your unclear point to this section.
:apprehend, v. - Oxford English Dictionary.
https://www.oed.com/viewdictionaryentry/Entry/9799
:understand. on the weblio.
https://ejje.weblio.jp/content/understand
:apprehend. on the weblio.
https://ejje.weblio.jp/content/apprehend
:comprehend. on the weblio.
https://ejje.weblio.jp/content/comprehend
:grasp. on the weblio.
https://ejje.weblio.jp/content/grasp
:GT.
https://translate.google.co.jp/?hl=ja&sl=ja&tl=en&op=translate