FA2020 p 612 has early fetal development. Here are the explanations for the answers:

• The syncytiotrophoblast mediates early implantation in the first week and this is when hCG secretion begins. Further, it forms concuttently with the cytotrophoblast from the trophoblast.
• The bilaminar disc (two layers) is present during week two, and gastrulation occurs during week 3 and 3 germ layers are the product.
• The neural tube is not fully formed until day 21 but the neural plate is formed on day 18 (FA2020 p490)
• The embryo is NOT resistant to teratogens here, neural tube defects can occur if the embry is exposed to teratogens in week 3. Earlier than this the embryo is in an "all or nothing" stage and death of the embryo is more likely to occur if the embryo is exposed.
• The somites form adjacent to the neural groove prior to sclerotome migration.

Basically, even without knowing all the exact days of development, most answers can be eliminated based on having the events in the incorrect order or having an incorrect aspect about development (i.e. the syncytiotrophoblast forms concurrent with the cytotrophobast, 3 germ layers are present after gastrulation, the embryo is never truly resistant to teratogens after implantation, the sclerotome forms from somites so somites have to come first).

Here is a general overview of the first three weeks of development after fertilization.

Here is another one if that doesn't do it for ya.