Platform costs or plans?

Hello good morning, I have a NodeMCU device with three temperature sensors and everything works perfectly with the platform but I have the following doubts:

Does the use of the platform have any price or plan? Which are? If the answer were yes.
How much data can I send and during what time interval?
Can I configure the device to send the temperature data in a time interval? example every 20 seconds

Thanks for your attention.

Cayenne free to use for home and small projects.

Have look at this topic Sending MQTT messages within rate limits

Thank you for your answers @shramik_salgaonkar