Not as such. But there were stronger and weaker cohorts.
When a Roman legion of this period deployed for battle, the default formation was to arrange the cohorts in two rows from right to left. That is, the first and sixth cohorts would be on the right flank, while the fifth and tenth on the left. See the following illustration from Vox:
As you deduced, one ...
Historians debate this, as what surviving Latin documents we have are either ambiguous; or presuppose knowledge which has been lost over time; or both.
Beyond the broad layout as (depending on period) cohorts, maniples, and centuries, in lines of hastati, principes and triarii in the earlier period, we know little beyond Caesar choosing to &...
I am imagining the picture is stylized and not drawn to scale.
Depending on how close the shield on the ramp was placed to the gates of the city, the shield would do two things:
Offer some protection to the attacking side from arrows and other
projectiles dispatched by the defenders.
Hide the attackers from the defenders so the defenders didn't know