It starts at the death of the testator. However the testament was given while Jesus was still alive, spoken to the Apostles which He then commanded them to go into all nations starting from Judea to teach.
How could something be given when it hadn't happened yet ? your literally adding to and contradicting that verse.
. How could they have been preaching the death ,burial and resurrection, when they did not understand it when Jesus told them., before it had even happened? it was kept from them ( luke 18
31¶Then he took
unto him the twelve, and said unto them, Behold, we go up to Jerusalem, and all things that are written by the prophets concerning the Son of man shall be accomplished.
32For he shall be delivered unto the Gentiles, and shall be mocked, and spitefully entreated, and spitted on:
33And they shall scourge
him, and put him to death: and the third day he shall rise again.
34¶And they understood none of these things: and this saying was hid from them, neither knew they the things which were spoken. ( This is way after they have been preaching , so its not the death, burial and resurrection that they are preaching is it ? )
,because had they understood, then Satan would have known and not incited the crucifiction . 1cor 2.8 Which none of the princes of this world knew: for had they known it, they would not have crucified the Lord of glory.