IPMI - is it possible to boot a server
Solution 1:
IPMI is a network protocol. What it CAN do depends not only on it, but also on how it is implemented.
If you have a BMC that is working even if the computer is off AND it allows to power control the machine - yes. This is standard for any BMC I have ever seen, but some cheap ones out there may not support it.
Often you do not use IPMI even most of the time - you can use a website or some web services to start the machine, using the controller board (redfish)
Solution 2:
If there is power to the BMC, then yes.