Cloud build with custom defaults

I have a few inquiries regarding the BUILD API endpoint of https://build.betaflight.com/api/builds.
But, I'm not sure if this is the appropriate place to post this question.

1) Where can I get more information about available build request params with their descriptions?
-> For example,
I couldn't find out what the '[classicBuild](https://github.com/search?q=org%3Abetaflight+classicBuild)' option is.
I'm not sure what '[configHash](https://github.com/search?q=org%3Abetaflight+configHash)' or 'Hash' from the response. is that for get DEFAULT plain text config from hash or build request key even if user does not submit to /support endpoint request?

2) Any way to create binary that includes predefined custom defaults while making a cloud build request endpoint?
-> For example, Wish to submit`Request parts` with custom `Config parts`:
```json
{
"Target": "already_in_configs_repo_target",
"Release": "4.5.2",
"Options": [
"CLOUD_BUILD",
"USE_SERIALRX_CRSF",
"USE_TELEMETRY_CRSF",
"USE_SERIALRX_SBUS",
"USE_DSHOT",
"USE_OSD_HD"
],
"Config": {
"Configuration": [
"resource BEEPER 1 NONE",
"feature RX_SERIAL",
"serial 1 64 115200 57600 0 115200",
"set serialrx_provider = sbus",
"set serialrx_inverted = off",
"set serialrx_halfduplex = off",
"set motor_pwm_protocol = dshot300",
"set dshot_bidir = off"
]
}
}
```

Start at the BUILD API endpoint and trace the request and response definitions for classicBuild, configHash, Hash, and Config.Configuration. Determine whether custom configuration defaults are supported by the shown request shape, and document the available parameters and the supported way to produce such a build.

Written by the indexing model from the issue text.