For learning purpose, C2 has a magnificient manual
, that also covers C2's SDK
Read again the check failure reported it indicates what part of the code you need to modify.
Apparently, the flags for the plugin in the edittime.js are not right.
It's unlikely that the plugin should work in r90 as the only SDK change between r90 and r91 was about dependencies. And the type of the object and the plugins flags are not related to that (or at least I don't think), so in theory, even r90 should be raising up check failures on run.
Anyway, just follow the SDK manual to clear up the code of your plugin.
About arrays, you can find about it in the dedicated manual article
and look for example of use listed in the how do I FAQ
under the section "Arrays".
About tokenat and other alike system expressions be sure to check the system references