Facebook deactivation/reactivation questions?

[HI *__*]

So I would like to deactivate my facebook for maybe a month or so, but then I want to reactivate it (I have exams and I feel it's the best way to not get distracted- woops).
I was wondering if once I reactivate it, will my chat history still be visible to me and everyone else I talked to? Like can I see old conversations with my friends?

And will comments, likes, etc be deleted and then will they reappear when I reactivate my account?

Thank you so much for your help x
Have a lovely Sunday
update:
i also read something somewhere about a 15-day period? someone care to explain what that is?