DeFi On-chain interaction

[DTverdov]

Hello Stars Lab's team, it's probably not an issue, but my help request to team. I'm working on adding heco to DeFi project for staking, and can not find in documentation answers on few important questions:

1. Which contracts and methods I can use to get claimable staking rewards and claim it;
2. Also I didn't find ability to do partial unstaking, unstake method on Validators contract doesn't accept unstake amount. Is there some way to do partial unstaking?
3. How I can calculate staking APR for specific validator?

P.S. sorry that make it as an issue, but I left my question in discord technical-help channel 2 days ago but didn't get any answer, I will close this issue as soon as get answers on most important questions for me.