If you start Steel Path Circuit prior to the reset, and hit tier 10 after the reset has occurred, you do get the rewards for hitting tier 10

I don't really have a good screenshot as proof, but I did some last minute tiering up in Steel Path Circuit prior to the reset and did two objectives past reset and hit tier 10, then extracted.

After extracting, upon viewing the Steel Path Circuit track it auto granted me the remaining rewards I hadn't claimed yet — including the tier 10 reward Incarnon I had selected.

https://i.imgur.com/5RJCZOY.png

This likely applies to Normal Circuit too.

submitted by /u/rickgibbed
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source https://www.reddit.com/r/Warframe/comments/1347lg3/if_you_start_steel_path_circuit_prior_to_the/