I'm new and I have questions about how the key time works, 30 days, 3 months and lifetime

[EMO3129]

I'm new and I have questions about how the key time works, 30 days, 3 months and lifetime.
How are the 30 days counted? from the first access or the payment date?

in the case of lifetime and if I change computers over time will I lose the key or do I need to buy again for a new PC?
I'm from Brazil and I use Google Translate, if I get confused I'm sorry