A schematic of the solution is shown below. The information
from the question is given in **black**. Deductions directly from this
information are given in **red**. Points that provide potential key information
are shown in **green** which leads to the structures which are linked via
the **blue** arrows to show the path required to work them all out. There
are, of course, other possible thought pathways.

Note that **A-D** do not contain chirality centers, whereas
**E-G** do.

The crux of this problem is reaction recognition..... ozonolysis, esterification, intramolecular Claisen condensation, alkylation and decarboxylation are all there.

Alternatively, once you get that **B** is a cyclic alkene, if you know it
is C6 then there is only one possible structure with a total of 3C types but
only 1 type of vinyl C.

From **B** then **C** and **D** are obtained.