1- beforehand is that correct max number of vcpu that a vm can support FT is 4vcpu ?
Yes, see:
2- is your means from primary = protected vm and secondary = shadow of protected vm ?
Yes.
3- you said ' the maximum number of FT VMs (primary or secondary) is 4 and sum of vCPU should be no more than 8 vCPU '
is that your means just 1vm with 4vcpu or 2vm with 2vcpu or 4vm with 1vcpu can be put on an esxi and Protected?
No, you can can 2 VMs with 4 vCPUs, or 4 VMs with 2 vCPU... and VMs can be either primary (protected) or secondary (shadow)... this is just math... the maximum number of VMs is 4 and the sum of vCPU is 8, no matter how you configure your VMs, of course you can't assign more than 4 vCPU per VM.
