Legally speaking and not talking about aircraft capability.Is it correct to set climb thrust before Flaps retraction Altitude which corresponds to the 3rd segment.
AFAIK, no. I have not seen a situation where thrust is reduced until clean with OEI.
In the 747, when AEO acceleration height is 1000', the thrust reduction is at flap retraction to 5 (T/O flap is 10 or 20). If an engine fails prior to 1000', T/O thrust is held until clean.