Validity of Free Plan

General
1

I just want to ask the validity of free plan ?
Is there any restriction on free plan ?
And the mentioned service in free plan are all per month or annually ?

Thanks

2 
Is there any restriction on free plan ?

Yes, there are, you can see them here: https://backendless.com/pricing/backendless-cloud-functional-limits/

And the mentioned service in free plan are all per month or annually ?

Per month.