Hello everyone. Is it possible to configure a 100G port broke out as 2x40G?
No that configuration is not valid (and is not valid per QSFP28 standard).
You have either 1x100G, 1x40G or 4x10G on the QSFP28 on a MX204.
For reference most switches will support breakout of a QSFP28 ports into 2x50G or 4x25G.